NAME
    Module::Generic - Generic Module to inherit from

SYNOPSIS
        package MyModule;
        BEGIN
        {
            use strict;
            use warnings;
            use parent qw( Module::Generic );
        };

        sub init
        {
            my $self = shift( @_ );
            # Requires parameters provided to have their equivalent method
            $self->{_init_strict_use_sub} = 1;
            # Smartly accepts key-value pairs as list or hash reference
            $self->SUPER::init( @_ );
            # This won't be affected by parameters provided during instantiation
            $self->{_private_param} = 'some value';
            return( $self );
        }
    
        sub active { return( shift->_set_get_boolean( 'active', @_ ) ); }
        sub address { return( shift->_set_get_object( 'address', 'My::Address', @_ ) ); }
        sub age { return( shift->_set_get_number( 'age', @_ ) ); }
        sub name { return( shift->_set_get_scalar( 'name', @_ ) ); }
        sub uuid { return( shift->_set_get_uuid( 'uuid', @_ ) ); }
        sub remote_addr { return( shift->_set_get_ip( 'remote_addr', @_ ) ); }
        sub discount
        {
            return( shift->_set_get_class_array( 'discount',
            {
            amount      => { type => 'number' },
            discount    => { type => 'object', class => 'My::Discount' },
            }, @_ ) );
        }
        sub settings 
        {
            return( shift->_set_get_class( 'settings',
            {
            # Will create a Module::Generic::Array array object of objects of class MY::Item
            items => { type => 'object_array_object', class => 'My::Item' },
            notify => { type => 'boolean' },
            resumes_at => { type => 'datetime' },
            timeout => { type => 'integer' },
            customer => {
                    definition => {
                        billing_address => { package => "My::Address", type => "object" },
                        email => { type => "scalar" },
                        name => { type => "scalar" },
                        shipping_address => { package => "My::Address", type => "object" },
                    },
                    type => "class",
                },
            }, @_ ) );
        }

VERSION
        v0.31.1

DESCRIPTION
    Module::Generic as its name says it all, is a generic module to inherit
    from. It is designed to provide a useful framework and speed up coding
    and debugging. It contains standard and support methods that may be
    superseded by your module.

    It also contains an AUTOLOAD transforming any hash object key into
    dynamic methods and also recognize the dynamic routine a la AutoLoader.
    The reason is that while "AutoLoader" provides the user with a
    convenient AUTOLOAD, I wanted a way to also keep the functionnality of
    Module::Generic AUTOLOAD that were not included in "AutoLoader". So the
    only solution was a merger.

METHODS
  import
    import() is used for the AutoLoader mechanism and hence is not a public
    method. It is just mentionned here for info only.

  new
    new will create a new object for the package, pass any argument it might
    receive to the special standard routine init that *must* exist. Then it
    returns what returns "init".

    To protect object inner content from sneaking by third party, you can
    declare the package global variable *OBJECT_PERMS* and give it a Unix
    permission, but only 1 digit. It will then work just like Unix
    permission. That is, if permission is 7, then only the module who
    generated the object may read/write content of the object. However, if
    you set 5, the, other may look into the content of the object, but may
    not modify it. 7, as you would have guessed, allow other to modify the
    content of an object. If *OBJECT_PERMS* is not defined, permissions
    system is not activated and hence anyone may access and possibly modify
    the content of your object.

    If the module runs under mod_perl, and assuming you have set the
    variable "GlobalRequest" in your Apache configuration, it is recognised
    and a clean up registered routine is declared to Apache to clean up the
    content of the object.

    This methods calls "init", which does all the work of setting object
    properties and calling methods to that effect.

  as_hash
    This will recursively transform the object into an hash suitable to be
    encoded in json.

    It does this by calling each method of the object and build an hash
    reference with the method name as the key and the method returned value
    as the value.

    If the method returned value is an object, it will call its "as_hash"
    method if it supports it.

    It returns the hash reference built

  clear
    Alias for "clear_error"

  clear_error
    Clear all error from the object and from the available global variable
    $ERROR.

    This is a handy method to use at the beginning of other methods of
    calling package, so the end user may do a test such as:

        $obj->some_method( 'some arguments' );
        die( $obj->error() ) if( $obj->error() );

        # some_method() would then contain something like:
        sub some_method
        {
            my $self = shift( @_ );
            ## Clear all previous error, so we may set our own later one eventually
            $self->clear_error();
            # ...
        }

    This way the end user may be sure that if "$obj-"error()> returns true
    something wrong has occured.

  clone
    Clone the current object if it is of type hash or array reference. It
    returns an error if the type is neither.

    It returns the clone.

  colour_close
    The marker to be used to set the closing of a command line colour
    sequence.

    Defaults to ">"

  colour_closest
    Provided with a colour, this returns the closest standard one supported
    by terminal.

    A colour provided can be a colour name, or a 9 digits rgb value or an
    hexadecimal value

  colour_format
    Provided with a hash reference of parameters, this will return a string
    properly formatted to display colours on the command line.

    Parameters are:

    *text* or *message*
        This is the text to be formatted in colour.

    *bgcolour* or *bgcolor* or *bg_colour* or *bg_color*
        The value for the background colour.

    *colour* or *color* or *fg_colour* or *fg_color* or *fgcolour* or
    *fgcolor*
        The value for the foreground colour.

        Valid value can be a colour name, an rgb value like 255255255, a rgb
        annotation like "rgb(255, 255, 255)" or a rgba annotation like
        "rgba(255,255,255,0.5)"

        A colour can be preceded by the words "light" or "bright" to provide
        slightly lighter colour where supported.

        Similarly, if an rgba value is provided, and the opacity is less
        than 1, this is equivalent to using the keyword "light"

        It returns the text properly formatted to be outputted in a
        terminal.

    *style*
        The possible values are: *bold*, *italic*, *underline*, *blink*,
        *reverse*, *conceal*, *strike*

  colour_open
    The marker to be used to set the opening of a command line colour
    sequence.

    Defaults to "<"

  colour_parse
    Provided with a string, this will parse the string for colour
    formatting. Formatting can be encapsulated in another formatting, and
    can be expressed in 2 different ways. For example:

        $self->colour_parse( "And {style => 'i|b', color => green}what about{/} {style => 'blink', color => yellow}me{/} ?" );

    would result with the words "what about" in italic, bold and green
    colour and the word "me" in yellow colour blinking (if supported).

    Another way is:

        $self->colour_parse( "And {bold light red on white}what about{/} {underline yellow}me too{/} ?" );

    would return a string with the words "what about" in light red bold text
    on a white background, and the words "me too" in yellow with an
    underline.

        $self->colour_parse( "Hello {bold red on white}everyone! This is {underline rgb(0,0,255)}embedded{/}{/} text..." );

    would return a string with the words "everyone! This is" in bold red
    characters on white background and the word "embedded" in underline blue
    color

    The idea for this syntax, not the code, is taken from Term::ANSIColor

  colour_to_rgb
    Convert a human colour keyword like "red", "green" into a rgb
    equivalent.

  coloured
    Provided with a colouring preference expressed as the first argument as
    string, and followed by 1 or more arguments that are concatenated to
    form the text string to format. For example:

        print( $o->coloured( 'bold white on red', "Hello it's me!\n" ) );

    A colour can be expressed as a rgb, such as :

        print( $o->coloured( 'underline rgb( 0, 0, 255 ) on white', "Hello everyone!" ), "\n" );

    rgb can also be rgba with the last decimal, normally an opacity used
    here to set light color if the value is less than 1. For example :

        print( $o->coloured( 'underline rgba(255, 0, 0, 0.5)', "Hello everyone!" ), "\n" );

  debug
    Set or get the debug level. This takes and return an integer.

    Based on the value, "message" will or will not print out messages. For
    example :

        $self->debug( 2 );
        $self->message( 2, "Debugging message here." );

    Since 2 used in "message" is equal to the debug value, the debugging
    message is printed.

    If the debug value is switched to 1, the message will be silenced.

  deserialise
        my $ref = $self->deserialise( %hash_of_options );
        my $ref = $self->deserialise( $hash_reference_of_options );
        my $ref = $self->deserialise( $serialised_data, %hash_of_options );
        my $ref = $self->deserialise( $serialised_data, $hash_reference_of_options );

    This method use a specified serialiser class and deserialise the given
    data either directly from a specified file or being provided, and
    returns the perl data.

    The serialisers currently supported are: CBOR::Free, CBOR::XS, JSON,
    Sereal and Storable::Improved (or the legacy Storable). They are not
    required by Module::Generic, so you must install them yourself. If the
    serialiser chosen is not installed, this will set an errr and return
    "undef".

    It takes an hash or hash reference of options. You can also provide the
    data to deserialise as the first argument followed by an hash or hash
    reference of options.

    It can then:

    *   retrieve data directly from File

    *   retrieve data from a file handle (only with Storable)

    *   Return the deserialised data

    The supported options are:

    *   "base64"

        Thise can be set to a true value like 1, or to your preferred base64
        encoder/decoder, or to an array reference containing 2 code
        references, the first one for encoding and the second one for
        decoding.

        If this is set simply to a true value, "deserialise" will call
        "_has_base64" to find out any installed base64 modules. Currently
        the ones supported are: Crypt::Misc and MIME::Base64. Of course, you
        need to have one of those modules installed first before it can be
        used.

        If this option is set and no appropriate module could be found,
        "deserialise" will return an error.

    *   "data"

        Data to be deserialised.

    *   "file"

        Provides a file path from which to read the serialised data.

    *   "io"

        A file handle. This is used when the serialiser is Storable to call
        its function "store_fd" in Storable::Improved and "fd_retrieve" in
        Storable::Improved

    *   *lock*

        Boolean. If true, this will lock the file before reading from it.
        This works only in conjonction with *file* and the serialiser
        Storable::Improved

    *   "serialiser"

        Specify the class name of the serialiser to use. Supported
        serialiser can either be "CBOR" or CBOR::XS, Sereal and Storable

        If the serialiser is CBOR::XS the following additional options are
        supported: "max_depth", "max_size", "allow_unknown",
        "allow_sharing", "allow_cycles", "forbid_objects", "pack_strings",
        "text_keys", "text_strings", "validate_utf8", "filter"

        See CBOR::XS for detail on those options.

        If the serialiser is Sereal, the following additional options are
        supported: "refuse_snappy", "refuse_objects", "no_bless_objects",
        "validate_utf8", "max_recursion_depth", "max_num_hash_entries",
        "max_num_array_entries", "max_string_length",
        "max_uncompressed_size", "incremental", "alias_smallint",
        "alias_varint_under", "use_undef", "set_readonly",
        "set_readonly_scalars"

        See Sereal for detail on those options.

    If an error occurs, this sets an error and return "undef"

  deserialize
    Alias for "deserialise"

  dump
    Provided with some data, this will return a string representation of the
    data formatted by Data::Printer

  dump_hex
    Returns an hexadecimal dump of the data provided.

    This requires the module Devel::Hexdump and will return "undef" and set
    an "error" if not found.

  dump_print
    Provided with a file to write to and some data, this will format the
    string representation of the data using Data::Printer and save it to the
    given file.

  dumper
    Provided with some data, and optionally an hash reference of parameters
    as last argument, this will create a string representation of the data
    using Data::Dumper and return it.

    This sets Data::Dumper to be terse, to indent, to use "qq" and
    optionally to not exceed a maximum *depth* if it is provided in the
    argument hash reference.

  dumpto
    Alias for "dumpto_dumper"

  printer
    Same as "dumper", but using Data::Printer to format the data.

  dumpto_printer
    Same as "dump_print" above that is an alias of this method.

  dumpto_dumper
    Same as "dumpto_printer" above, but using Data::Dumper

  errno
    Sets or gets an error number.

  error
    Provided with a list of strings or an hash reference of parameters and
    this will set the current error issuing a Module::Generic::Exception
    object, call "warn" in perlfunc, or "$r-"warn> under Apache2 modperl,
    and returns undef() or an empty list in list context:

        if( $some_condition )
        {
            return( $self->error( "Some error." ) );
        }

    Note that you do not have to worry about a trailing line feed sequence.
    "error" takes care of it.

    The script calling your module could write calls to your module methods
    like this:

        my $cust_name = $object->customer->name ||
            die( "Got an error in file ", $object->error->file, " at line ", $object->error->line, ": ", $object->error->trace, "\n" );
        # or simply:
        my $cust_name = $object->customer->name ||
            die( "Got an error: ", $object->error, "\n" );

    If you want to use an hash reference instead, you can pass the following
    parameters. Any other parameters will be passed to the exception class.

    *class*
        The package name or class to use to instantiate the error object. By
        default, it will use Module::Generic::Exception class or the one
        specified with the object property "_exception_class"

            $self->do_something_bad ||
                return( $self->error({
                    code => 500,
                    message => "Oopsie",
                    class => "My::NoWayException",
                }) );
            my $exception = $self->error; # an My::NoWayException object

        Note, however, that if the class specified cannot be loaded for some
        reason, "error" in Module::Generic will die since this would be an
        error within another error.

    *message*
        The error message.

    *want*
        An array reference of data types that you allow this method to
        return when such data type is expected by the original caller.

        Supported data types are: "ARRAY", "CODE", "GLOB", "HASH", "OBJECT",
        "SCALAR"

        Note that, actually, the data type you provide is case insensitive.

        For example, you have a method that returns an array, but an error
        occurs, and it returns "undef" instead:

            sub your_method
            {
                my $self = shift( @_ );
                return( $self->error( "Something is wrong" ) ) if( $self->something_is_missing );
                return( $self->{array} );
            }

            my $array = $obj->your_method; # array is undef

        If the user does:

            $obj->your_method->[0]; # perl error occurs

        This would trigger a perl error "Can't use an undefined value as an
        ARRAY reference", which may be fine if this is what you want, but if
        you want instead to ensure the user does not get an error, but
        instead an empty array, in your method "your_method", you could
        write this "your_method" this way instead, passing the "want"
        parameter:

            sub your_method
            {
                my $self = shift( @_ );
                return( $self->error( { message => "Something is wrong", want => [qw( array )] ) ) if( $self->something_is_missing );
                return( $self->{array} );
            }

        Then, if the user calls this method in array context and an error
        occurs, it would now return instead an empty array.

            my $array = $obj->your_method->[0]; # undef

        Note that, by default, the "object" call context is always
        activated, so you do not have to specify it.

    Note also that by calling "error" it will not clear the current error.
    For that you have to call "clear_error" explicitly.

    Also, when an error is set, the global variable *ERROR* in the
    inheriting package is set accordingly. This is especially usefull, when
    your initiating an object and that an error occured. At that time, since
    the object could not be initiated, the end user can not use the object
    to get the error message, and then can get it using the global module
    variable *ERROR*, for example:

        my $obj = Some::Package->new ||
        die( $Some::Package::ERROR, "\n" );

    If the caller has disabled warnings using the pragma "no warnings",
    "error" will respect it and not call warn. Calling warn can also be
    silenced if the object has a property *quiet* set to true.

    The error message can be split in multiple argument. "error" will
    concatenate each argument to form a complete string. An argument can
    even be a reference to a sub routine and will get called to get the
    resulting string, unless the object property *_msg_no_exec_sub* is set
    to false. This can switched off with the method "noexec"

    If perl runs under Apache2 modperl, and an error handler is set with
    "error_handler", this will call the error handler with the error string.

    If an Apache2 modperl log handler has been set, this will also be called
    to log the error.

    If the object property *fatal* is set to true, this will call die
    instead of "warn" in perlfunc.

    Last, but not least since "error" returns undef in scalar context or an
    empty list in list context, if the method that triggered the error is
    chained, it would normally generate a perl error that the following
    method cannot be called on an undefined value. To solve this, when an
    object is expected, "error" returns a special object from module
    Module::Generic::Null that will enable all the chained methods to be
    performed and return the error when requested to. For example:

        my $o = My::Package->new;
        my $total $o->get_customer(10)->products->total || die( $o->error, "\n" );

    Assuming this method here "get_customer" returns an error, the chaining
    will continue, but produce nothing and ultimately returns undef.

  error_handler
    Sets or gets a code reference that will be called to handle errors that
    have been triggered when calling "error"

  errors
    Used by error() to store the error sent to him for history.

    It returns an array of all error that have occured in lsit context, and
    the last error in scalar context.

  errstr
    Set/get the error string, period. It does not produce any warning like
    error would do.

  fatal
    Boolean. If enabled, any error will call "die" in perlfunc instead of
    returning "undef" in perlfunc and setting an error.

    Defaults to false.

    You can enable it in your own package by initialising it in your own
    "init" method like this:

        sub init
        {
            my $self = shift( @_ );
            $self->{fatal} = 1;
            return( $self->SUPER::init( @_ ) );
        }

  get
    Uset to get an object data key value:

        $obj->set( 'verbose' => 1, 'debug' => 0 );
        ## ...
        my $verbose = $obj->get( 'verbose' );
        my @vals = $obj->get( qw( verbose debug ) );
        print( $out "Verbose level is $vals[ 0 ] and debug level is $vals[ 1 ]\n" );

    This is no more needed, as it has been more conveniently bypassed by the
    AUTOLOAD generic routine with which you may say:

        $obj->verbose( 1 );
        $obj->debug( 0 );
        ## ...
        my $verbose = $obj->verbose();

    Much better, no?

  init
    This is the "new" package object initializer. It is called by "new" and
    is used to set up any parameter provided in a hash like fashion:

        my $obj My::Module->new( 'verbose' => 1, 'debug' => 0 );

    You may want to superseed "init" to have it suit your needs.

    "init" needs to returns the object it received in the first place or an
    error if something went wrong, such as:

        sub init
        {
            my $self = shift( @_ );
            my $dbh  = DB::Object->connect() ||
            return( $self->error( "Unable to connect to database server." ) );
            $self->{dbh} = $dbh;
            return( $self );
        }

    In this example, using "error" will set the global variable $ERROR that
    will contain the error, so user can say:

        my $obj = My::Module->new() || die( $My::Module::ERROR );

    If the global variable *VERBOSE*, *DEBUG*, *VERSION* are defined in the
    module, and that they do not exist as an object key, they will be set
    automatically and accordingly to those global variable.

    The supported data type of the object generated by the "new" method may
    either be a hash reference or a glob reference. Those supported data
    types may very well be extended to an array reference in a near future.

    When provided with an hash reference, and when object property
    *_init_strict_use_sub* is set to true, "init" will call each method
    corresponding to the key name and pass it the key value and it will set
    an error and skip it if the corresponding method does not exist.
    Otherwise, it calls each corresponding method and pass it whatever value
    was provided and check for that method return value. If the return value
    is "undef" in perlfunc and the value provided is not itself "undef",
    then it issues a warning and return the "error" that is assumed having
    being set by that method.

    Otherwise if the object property *_init_strict* is set to true, it will
    check the object property matching the hash key for the default value
    type and set an error and return undef if it does not match. Foe
    example, "init" in your module could be like this:

        sub init
        {
            my $self = shift( @_ );
            $self->{_init_strict} = 1;
            $self->{products} = [];
            return( $self->SUPER::init( @_ ) );
        }

    Then, if init is called like this:

        $object->init({ products => $some_string_but_not_array }) || die( $object->error, "\n" );

    This would cause your script to die, because "products" value is a
    string and not an array reference.

    Otherwise, if none of those special object properties are set, the init
    will create an object property matching the key of the hash and set its
    value accordingly. For example :

        sub init
        {
            my $self = shift( @_ );
            return( $self->SUPER::init( @_ ) );
        }

    Then, if init is called like this:

        $object->init( products => $array_ref, first_name => 'John', last_name => 'Doe' });

    The object would then contain the properties *products*, *first_name*
    and *last_name* and can be accessed as methods, such as :

        my $fname = $object->first_name;

    You can also alter the way "init" process the parameters received using
    the following properties you can set in your own "init" method, for
    example:

        sub init
        {
            my $self = shift( @_ );
            # Set the order in which the parameters are processed, because some methods may rely on other methods' value
            $self->{_init_params_order} [qw( method1 method2 )];
            # Enable strict sub, which means the corresponding method must exist for the parameter provided
            $self->{_init_strict_use_sub} = 1;
            # Set the class name of the exception to use in error()
            # Here My::Package::Exception should inherit from Module::Generic::Exception or some other Exception package
            $self->{_exception_class} = 'My::Package::Exception';
            $self->SUPER::init( @_ ) || return( $self->pass_error );
            return( $self );
        }

    You can also specify a default exception class that will be used by
    "error" to create exception object, by setting the object property
    "_exception_class":

        sub init
        {
            my $self = shift( @_ );
            $self->{name} = 'default_name';
            # For any key-value pairs to be matched by a corresponding method
            $self->{_init_strict_use_sub} = 1;
            $self->{_exception_class} = 'My::Exception';
            return( $self->SUPER::init( @_ ) );
        }

  log_handler
    Provided a reference to a sub routine or an anonymous sub routine, this
    will set the handler that is called by "message"

    It returns the current value set.

  message
    message() is used to display verbose/debug output. It will display
    something to the extend that either *verbose* or *debug* are toggled on.

    If so, all debugging message will be prepended by " ## " by default or
    the prefix string specified with the *prefix* option, to highlight the
    fact that this is a debugging message.

    Addionally, if a number is provided as first argument to message(), it
    will be treated as the minimum required level of debugness. So, if the
    current debug state level is not equal or superior to the one provided
    as first argument, the message will not be displayed.

    For example:

        # Set debugness to 3
        $obj->debug( 3 );
        # This message will not be printed
        $obj->message( 4, "Some detailed debugging stuff that we might not want." );
        # This will be displayed
        $obj->message( 2, "Some more common message we want the user to see." );

    Now, why debug is used and not verbose level? Well, because mostly, the
    verbose level needs only to be true, that is equal to 1 to be efficient.
    You do not really need to have a verbose level greater than 1. However,
    the debug level usually may have various level.

    Also, the text provided can be separated by comma, and even be a code
    reference, such as:

        $self->message( 2, "I have found", "something weird here:", sub{ $self->dumper( $data ) } );

    If the object has a property *_msg_no_exec_sub* set to true, then a code
    reference will not be called and instead be added to the string as is.
    This can be done simply like this:

        $self->noexec->message( 2, "I have found", "something weird here:", sub{ $self->dumper( $data ) } );

    "message" also takes an optional hash reference as the last parameter
    with the following recognised options:

    *caller_info*
        This is a boolean value, which is true by default.

        When true, this will prepend the debug message with information
        about the caller of "message"

    *level*
        An integer. Debugging level.

    *message*
        The text of the debugging message. This is optional since this can
        be provided as first or consecutive arguments like in a list as
        demonstrated in the example above. This allows you to do something
        like this:

            $self->message( 2, { message => "Some debug message here", prefix => ">>" });

        or

            $self->message( { message => "Some debug message here", prefix => ">>", level => 2 });

    *no_encoding*
        Boolean value. If true and when the debugging is set to be printed
        to a file, this will not set the binmode to "utf-8"

    *prefix*
        By default this is set to "##". This value is used as the prefix
        used in debugging output.

    *type*
        Type of debugging

  message_check
    This is called by "message"

    Provided with a list of arguments, this method will check if the first
    argument is an integer and find out if a debug message should be printed
    out or not. It returns the list of arguments as an array reference.

  message_color
    Alias for "message_colour"

  message_colour
    This is the same as "message", except this will check for colour
    formatting, which "message" does not do. For example:

        $self->message_colour( 3, "And {bold light white on red}what about{/} {underline green}me again{/} ?" );

    "message_colour" can also be called as message_color

    See also "colour_format" and "colour_parse"

  message_frame
    Return the optional hash reference of parameters, if any, that can be
    provided as the last argument to "message"

  messagef
    This works like "sprintf" in perlfunc, so provided with a format and a
    list of arguments, this print out the message. For example :

        $self->messagef( 1, "Customer name is %s", $cust->name );

    Where 1 is the debug level set with "debug"

  messagef_colour
    This method is same as "message_colour" and messagef combined.

    It enables to pass sprintf-like parameters while enabling colours.

  message_log
    This is called from "message".

    Provided with a message to log, this will check if "message_log_io"
    returns a valid file handler, presumably to log file, and if so print
    the message to it.

    If no file handle is set, this returns undef, other it returns the value
    from "$io-"print>

  message_log_io
    Set or get the message log file handle. If set, "message_log" will use
    it to print messages received from "message"

    If no argument is provided bu your module has a global variable
    "LOG_DEBUG" set to true and global variable "DEB_LOG" set presumably to
    the file path of a log file, then this attempts to open in write mode
    the log file.

    It returns the current log file handle, if any.

  new_array
    Instantiate a new Module::Generic::Array object. If any arguments are
    provided, it will pass it to "new" in Module::Generic::Array and return
    the object.

  new_datetime
    Provided with some optional arguments and this will instantiate a new
    Module::Generic::DateTime object, passing it whatever argument was
    provided.

    Example:

        my $dt = DateTime->now( time_zone => 'Asia/Tokyo' );
        # Returns a new Module::Generic::DateTime object
        my $d = $o->new_datetime( $dt );

        # Returns a new Module::Generic::DateTime object with DateTime initiated automatically
        # to now with time zone set by default to UTC
        my $d = $o->new_datetime;

  new_file
    Instantiate a new Module::Generic::File object. If any arguments are
    provided, it will pass it to "new" in Module::Generic::File and return
    the object.

  new_glob
    This method is called instead of "new" in your package for GLOB type
    module.

    It will set an hash of options provided and call "init" and return the
    newly instantiated object upon success, or "undef" upon error.

  new_hash
    Instantiate a new Module::Generic::Hash object. If any arguments are
    provided, it will pass it to "new" in Module::Generic::Hash and return
    the object.

  new_json
    This method tries to load JSON and create a new object.

    By default it enables the following JSON object properties:

    "allow_blessed" in JSON
    "allow_nonref" in JSON
    "convert_blessed" in JSON
    "relaxed" in JSON

  new_null
    Returns a null value based on the expectations of the caller and thus
    without breaking the caller's call flow.

    You can also optionally provide an hash or hash reference containing the
    option "type" with a value being either "ARRAY", "CODE", "HASH",
    "OBJECT" or "SCALARREF" to force "new_null" to return the corresponding
    data without using the caller's context.

    If the caller wants an hash reference, it returns an empty hash
    reference.

    If the caller wants an array reference, it returns an empty array
    reference.

    If the caller wants a code reference, it returns an anonymous subroutine
    that returns "undef" or an empty list.

    If the caller is calling another method right after, this means this is
    an object context and "new_null" will instantiate a new
    Module::Generic::Null object. If any arguments were provided to
    "new_null", they will be passed along to "new" in Module::Generic::Null
    and the new object will be returned.

    In any other context, "undef" is returned or an empty list.

    Without using "new_null", if you return simply undef, like:

        my $val = $object->return_false->[0];
    
        sub return_false { return }

    The above would trigger an error that the value returned by
    "return_false" is not an array reference. Instead of checking on the
    recipient end what kind of returned value was returned, the caller only
    need to check if it is defined or not, no matter the context in which it
    is called.

    For example:

        my $this = My::Object->new;
        my $val  = $this->call1;
        # return undef)
    
        # object context
        $val = $this->call1->call_again;
        # $val is undefined
    
        # hash reference context
        $val = $this->call1->fake->{name};
        # $val is undefined
    
        # array reference context
        $val = $this->call1->fake->[0];
        # $val is undefined

        # code reference context
        $val = $this->call1->fake->();
        # $val is undefined

        # scalar reference context
        $val = ${$this->call1->fake};
        # $val is undefined

        # simple scalar
        $val = $this->call1->fake;
        # $val is undefined

        package My::Object;
        use parent qw( Module::Generic );

        sub call1
        {
            return( shift->call2 );
        }

        sub call2 { return( shift->new_null ); }

        sub call_again
        {
            my $self = shift( @_ );
            print( "Got here in call_again\n" );
            return( $self );
        }

    This technique is also used by "error" to set an error object and return
    undef but still allow chaining beyond the error. See "error" and
    Module::Generic::Exception for more information.

  new_number
    Instantiate a new Module::Generic::Number object. If any arguments are
    provided, it will pass it to "new" in Module::Generic::Number and return
    the object.

  new_scalar
    Instantiate a new Module::Generic::Scalar object. If any arguments are
    provided, it will pass it to "new" in Module::Generic::Scalar and return
    the object.

  new_tempdir
    Returns a new temporary directory by calling "tempdir" in
    Module::Generic::File

  new_tempfile
    Returns a new temporary directory by calling "tempfile" in
    Module::Generic::File

  new_version
    Provided with a version and this will return a new version object.

    If the value provided is not a suitable version, this will set an error
    and return "undef"

  noexec
    Sets the module property *_msg_no_exec_sub* to true, so that any call to
    "message" whose arguments include a reference to a sub routine, will not
    try to execute the code. For example, imagine you have a sub routine
    such as:

        sub hello
        {
            return( "Hello !" );
        }

    And in your code, you write:

        $self->message( 2, "Someone said: ", \&hello );

    If *_msg_no_exec_sub* is set to false (by default), then the above would
    print out the following message:

        Someone said Hello !

    But if *_msg_no_exec_sub* is set to true, then the same would rather
    produce the following :

        Someone said CODE(0x7f9103801700)

  pass_error
    Provided with an error, typically a Module::Generic::Exception object,
    but it could be anything as long as it is an object, hopefully an
    exception object, this will set the error value to the error provided,
    and without issuing any new warning nor creating a new
    Module::Generic::Exception object.

    It makes it possible to pass the error along so the caller can retrieve
    it later. This is typically used by a method calling another one in
    another module that produced an error. For example :

        sub getCustomerInfo
        {
            my $self = shift( @_ );
            # Maybe a LWP::UserAgent sub class?
            my $client = $self->lwp_client_object;
            my $res = $client->get( $remote_api_endpoint ) ||
                return( $self->pass_error( $client->error ) );
        }

    Then :

        my $client_info = $object->getCustomerInfo || die( $object->error, "\n" );

    Which would return the http client error that has been passed along

    You can optionally provide an hash of parameters as the last argument,
    such as:

        return( $self->pass_error( $obj->error, { class => 'My::Exception', code => 400 } ) );

    Supported options are:

    "class"
        The name of a class name to re-bless the error object provided.

    "code"
        The error code to set in the error object being passed.

  quiet
    Set or get the object property *quiet* to true or false. If this is
    true, no warning will be issued when "error" is called.

  save
    Provided with some data and a file path, or alternatively an hash
    reference of options with the properties *data*, *encoding* and *file*,
    this will write to the given file the provided *data* using the encoding
    *encoding*.

    This is designed to simplify the tedious task of write to files.

    If it cannot open the file in write mode, or cannot print to it, this
    will set an error and return undef. Otherwise this returns the size of
    the file in bytes.

  serialise
    This method use a specified serialiser class and serialise the given
    data either by returning it or by saving it directly to a given file.

    The serialisers currently supported are: CBOR::Free, CBOR::XS, JSON,
    Sereal and Storable::Improved (or the legacy version Storable). They are
    not required by Module::Generic, so you must install them yourself. If
    the serialiser chosen is not installed, this will set an errr and return
    "undef".

    This method takes some data and an optional hash or hash reference of
    parameters. It can then:

    *   save data directly to File

    *   save data to a file handle (only with Storable::Improved / Storable)

    *   Return the serialised data

    The supported parameters are:

    *   *append*

        Boolean. If true, the serialised data will be appended to the given
        file. This works only in conjonction with *file*

    *   *base64*

        Thise can be set to a true value like 1, or to your preferred base64
        encoder/decoder, or to an array reference containing 2 code
        references, the first one for encoding and the second one for
        decoding.

        If this is set simply to a true value, "serialise" will call
        "_has_base64" to find out any installed base64 modules. Currently
        the ones supported are: Crypt::Misc and MIME::Base64. Of course, you
        need to have one of those modules installed first before it can be
        used.

        If this option is set and no appropriate module could be found,
        "serialise" will return an error.

    *   *file*

        String. A file path where to store the serialised data.

    *   *io*

        A file handle. This is used when the serialiser is
        Storable::Improved / Storable to call its function "store_fd" in
        Storable::Improved and "fd_retrieve" in Storable::Improved

    *   *lock*

        Boolean. If true, this will lock the file before writing to it. This
        works only in conjonction with *file* and the serialiser
        Storable::Improved

    *   *serialiser* or *serializer*

        A string being the class of the serialiser to use. This can be only
        either Sereal or Storable::Improved

    Additionally the following options are supported and passed through
    directly for each serialiser:

    *   CBOR::Free: "canonical", "string_encode_mode",
        "preserve_references", "scalar_references"

    *   CBOR: "max_depth", "max_size", "allow_unknown", "allow_sharing",
        "allow_cycles", "forbid_objects", "pack_strings", "text_keys",
        "text_strings", "validate_utf8", "filter"

    *   JSON: "allow_blessed" "allow_nonref" "allow_unknown" "allow_tags"
        "ascii" "boolean_values" "canonical" "convert_blessed"
        "filter_json_object" "filter_json_single_key_object" "indent"
        "latin1" "max_depth" "max_size" "pretty" "relaxed" "space_after"
        "space_before" "utf8"

    *   "encode" in Sereal::Decoder if the serialiser is Sereal:
        "aliased_dedupe_strings", "canonical", "canonical_refs", "compress",
        "compress_level", "compress_threshold", "croak_on_bless",
        "dedupe_strings", "freeze_callbacks", "max_recursion_depth",
        "no_bless_objects", "no_shared_hashkeys", "protocol_version",
        "snappy", "snappy_incr", "snappy_threshold", "sort_keys",
        "stringify_unknown", "undef_unknown", "use_protocol_v1",
        "warn_unknown"

    *   Storable::Improved / Storable: no option available

    If an error occurs, this sets an error and return "undef"

  serialize
    Alias for "serialise"

  set
    set() sets object inner data type and takes arguments in a hash like
    fashion:

        $obj->set( 'verbose' => 1, 'debug' => 0 );

  subclasses
    Provided with a *CLASS* value, this method try to guess all the existing
    sub classes of the provided *CLASS*.

    If *CLASS* is not provided, the class into which was blessed the calling
    object will be used instead.

    It returns an array of subclasses in list context and a reference to an
    array of those subclasses in scalar context.

    If an error occured, undef is returned and an error is set accordingly.
    The latter can be retrieved using the error method.

  true
    Returns a "true" variable from Module::Generic::Boolean

  false
    Returns a "false" variable from Module::Generic::Boolean

  verbose
    Set or get the verbosity level with an integer.

  will
    This will try to find out if an object supports a given method call and
    returns the code reference to it or undef if none is found.

  AUTOLOAD
    The special AUTOLOAD() routine is called by perl when no matching
    routine was found in the module.

    AUTOLOAD() will then try hard to process the request. For example, let's
    assue we have a routine foo.

    It will first, check if an equivalent entry of the routine name that was
    called exist in the hash reference of the object. If there is and that
    more than one argument were passed to this non existing routine, those
    arguments will be stored as a reference to an array as a value of the
    key in the object. Otherwise the single argument will simply be stored
    as the value of the key of the object.

    Then, if called in list context, it will return a array if the value of
    the key entry was an array reference, or a hash list if the value of the
    key entry was a hash reference, or finally the value of the key entry.

    If this non existing routine that was called is actually defined, the
    routine will be redeclared and the arguments passed to it.

    If this fails too, it will try to check for an AutoLoadable file in
    "auto/PackageName/routine_name.al"

    If the filed exists, it will be required, the routine name linked into
    the package name space and finally called with the arguments.

    If the require process failed or if the AutoLoadable routine file did
    not exist, AUTOLOAD() will check if the special routine EXTRA_AUTOLOAD()
    exists in the module. If it does, it will call it and pass it the
    arguments. Otherwise, AUTOLOAD will die with a message explaining that
    the called routine did not exist and could not be found in the current
    class.

SUPPORT METHODS
    Those methods are designed to be called from the package inheriting from
    Module::Generic to perform various function and speed up development.

  __create_class
    Provided with an object property name and an hash reference representing
    a dictionary and this will produce a dynamically created class/module.

    If a property *_class* exists in the dictionary, it will be used as the
    class/package name, otherwise a name will be derived from the calling
    object class and the object property name. For example, in your module :

        sub products { return( 'products', shift->_set_get_class(
        {
        name        => { type => 'scalar' },
        customer    => { type => 'object', class => 'My::Customer' },
        orders      => { type => 'array_as_object' },
        active      => { type => 'boolean' },
        created     => { type => 'datetime' },
        metadata    => { type => 'hash' },
        stock       => { type => 'number' },
        url         => { type => 'uri' },
        }, @_ ) ); }

    Then calling your module method products such as :

        my $prod = $object->products({
            name => 'Cool product',
            customer => { first_name => 'John', last_name => 'Doe', email => 'john.doe@example.com' },
            orders => [qw( 123 987 456 654 )],
            active => 1,
            metadata => { transaction_id => 123, api_call_id => 456 },
            stock => 10,
            uri => 'https://example.com/p/20'
        });

    Using the resulting object $prod, we can access this dynamically created
    class/module such as :

        printf( <<EOT, $prod->name, $prod->orders->length, $prod->customer->last_name,, $prod->url->path )
        Product name: %s
        No of orders: %d
        Customer name: %s
        Product page path: %s
        EOT

  __instantiate_object
        my $o = $self->__instantiate_object( 'emails', 'Some::Module', @_ );
        # or, with a callback
        my $o = $self->__instantiate_object({ field => 'emails', callback => sub
        {
            my( $class, $args ) = @_;
            return( $class->parse_bare_address( $args->[0] ) );
        }}, 'Email::Address::XS', @_ );

    Provided with an object property name, and a class/package name, this
    will attempt to load the module if it is not already loaded. It does so
    using "load_class" in Class::Load. Once loaded, it will init an object
    passing it the other arguments received. It returns the object
    instantiated upon success or undef and sets an "error"

    This is a support method used by "_instantiate_object"

    Alternatively, you can pass an hash reference, instead of the object
    property name, with the following properties:

    *   "field"

        Mandatory. The object property name.

    *   "callback"

        Optional. A code reference like an anonymous subroutine that will be
        called with the class and an array reference of values provided, but
        possibly empty.

    This is a useful callback when the module instantiation either does not
    use the "new" method or does not simply take one or multiple arguments,
    such as when the instantiation method would require an hash of
    parameters, such as Email::Address::XS

  _instantiate_object
    This does the same thing as "__instantiate_object" and the purpose is
    for this method to be potentially superseded in your own module. In your
    own module, you would call "__instantiate_object"

  _can
    Provided with a value and a method name, and this will return true if
    the value provided is an object that "can" in UNIVERSAL perform the
    method specified, or false otherwise.

    You can also provide an array of method names to check instead of just a
    method name. In that case, all method names provided must be supported
    by the object otherwise it will return false.

    This makes it more convenient to write:

        if( $self->_can( $obj, 'some_method' ) )
        {
            # ...
        }

    or

        if( $self->_can( $obj, [qw(some_method other_method )] ) )
        {
            # ...
        }

    than to write:

        if( Scalar::Util::bless( $obj ) && $obj->can( 'some_method' )
        {
            # ...
        }

  _can_overload
        my $rv = $self->_can_overload( undef, '""' ); # false
        my $rv = $self->_can_overload( '', '""' ); # false
        my $rv = $self->_can_overload( $some_object_not_overloaded, '""' ); # false
        # In this example, it would return false, because, although it is an overloaded value provided, that object has no support for the operators specified.
        my $rv = $self->_can_overload( $some_object_overloaded, '""' ); # false
        my $rv = $self->_can_overload( $some_good_object_overloaded, '""' ); # true
        my $rv = $self->_can_overload( $some_good_object_overloaded, [ '""', 'bool' ] ); # true

    Provided with some value and a string representing an operator, or an
    array reference of operators, and this will return true if the value is
    an object that has the specified operator, or operators in case of an
    array reference of operators provided, overloaded.

    It returns false otherwise.

  _get_args_as_array
    Provided with arguments and this support method will return the
    arguments provided as an array reference irrespective of whether they
    were initially provided as array reference or a simple array.

    For example:

        my $array = $self->_get_args_as_array(qw( those are arguments ));
        # returns an array reference containing: 'those', 'are', 'arguments'
        my $array = $self->_get_args_as_array( [qw( those are arguments )] );
        # same result as previous example
        my $array = $self->_get_args_as_array(); # no args provided
        # returns an empty array reference

  _get_args_as_hash
    Provided with arguments and this support method will return the
    arguments provided as hash reference irrespective of whether they were
    initially provided as hash reference or a simple hash.

    In list context, this returns an hash reference and an array reference
    containing the order of the properties provided.

    For example:

        my $ref = $self->_get_args_as_hash( first => 'John', last => 'Doe' );
        # returns hash reference { first => 'John', last => 'Doe' }
        my $ref = $self->_get_args_as_hash({ first => 'John', last => 'Doe' });
        # same result as previous example
        my $ref = $self->_get_args_as_hash(); # no args provided
        # returns an empty hash reference
        my( $ref, $keys ) = $self->_get_args_as_hash( first => 'John', last => 'Doe' );

    In the last example, $keys is an array object containing the list of
    properties passed an in the order they were provided, i.e. "first" and
    "last". If the properties were provided as an hash reference, the $keys
    returned will be the sorted list of properties, such as:

        my( $ref, $keys ) = $self->_get_args_as_hash({ last => 'Doe', first => 'John' });

    Here, $keys will be sorted and contain the properties in their
    alphabetical order.

    However, this will return empty:

        my $ref = $self->_get_args_as_hash( { age => 42, city => 'Tokyo' }, some_other => 'parameter' );

    This returns an empty hash reference, because although the first
    parameter is an hash reference, there is more than one parameter.

    As of version v0.24.0, this utility method allows for more advanced use
    and permits embedding parameters among arguments, remove them from the
    list and return them.

    For example:

    Assuming @_ contains: "foo bar debug 4 baz"

        my $ref = $self->_get_args_as_hash( @_, args_list => [qw( debug )] );

    This will set $ref with "debug" only.

    Even the special parameter "args_list" does not have to be at the end
    and could be anywhere:

        my $ref = $self->_get_args_as_hash( 'foo', 'bar', args_list => [qw( debug )], 'debug', 4, 'baz' );

    If you want to modify @_,because you need its content without any
    params, pass @_ as an array reference.

        my $ref = $self->_get_args_as_hash( \@_, args_list => [qw( debug )] );
        say "@_";

    $ref is an hash reference that would contain "debug" and @_ only
    contains "foo bar baz"

    You can also simply pass @_ as a reference to simply save memory.

    Assuming @_ is "foo bar baz 3 debug 4"

        my $ref = $self->_get_args_as_hash( \@_ );

    This would set $ref to be an hash reference with keys "foo baz debug"

  _get_stack_trace
    This will return a Devel::StackTrace object initiated with the following
    options set:

    "indent" 1
        This will set an initial indent tab

    "skip_frames" 1
        This is set to 1 so this very method is not included in the frames
        stack

  _has_base64
    Provided with a value and this returns an array reference containing 2
    code references: one for encoding and one for decoding.

    Value provided can be a simple true value, such as 1, and then
    "_has_base64" will check if Crypt::Misc and MIME::Base64 are installed
    on the system and will use in priority MIME::Base64

    The value provided can also be an array reference already containing 2
    code references, and in such case, that value is simply returned.
    Nothing more is done.

    Finally, the value provided can be a module class name. "_has_base64"
    knows only of Crypt::Misc and MIME::Base64, so if you want to use any
    other one, arrange yourself to pass to "_has_base64" an array reference
    of 2 code references as explained above.

  _implement_freeze_thaw
    Provided with a list of package names and this method will implement in
    each of them the subroutines necessary to handle Storable::Improved (or
    the legacy Storable), CBOR and Sereal serialisation.

    In effect, it will check that the subroutines "FREEZE", "THAW",
    "STORABLE_freeze" and "STORABLE_thaw" exists or sets up simple ones if
    they are not defined.

    This works for packages that use hash-based objects. However, you need
    to make sure there is no specific package requirements, and if there is,
    you might need to customise those subroutines by yourself.

  _is_a
    Provided with an object and a package name and this will return true if
    the object is a blessed object from this package name (or a sub package
    of it), or false if not.

    The value of this is to reduce the burden of having to check whether the
    object actually exists, i.e. is not null or undef, if it is an object
    and if it is from that class. This allows to do it in just one method
    call like this:

        if( $self->_is_a( $obj, 'My::Package' ) )
        {
            # Do something
        }

    Of course, if you are sure the object is actually an object, then you
    can directly do:

        if( $obj->isa( 'My::Package' ) )
        {
            # Do something
        }

  _is_array
    Provided with some data, this checks if the data is of type array, even
    if it is an object.

    This uses "reftype" in Scalar::Util to achieve that purpose. So for
    example, an object such as :

        package My::Module;

        sub new
        {
            return( bless( [] => ( ref( $_[0] ) || $_[0] ) ) );
        }

    This would produce an object like :

        My::Module=ARRAY(0x7f8f3b035c20)

    When checked with "_is_array" this, would return true just like an
    ordinary array.

    If you would use :

        ref( $object );

    It would rather return the module package name: "My::Module"

  _is_class_loadable
    Takes a module name and an optional version number and this will check
    if the module exist and can be loaded by looking at the @INC and using
    version to compare required version and existing version.

    It returns true if the module can be loaded or false otherwise.

  _is_class_loaded
    Provided with a class/package name, this returns true if the module is
    already loaded or false otherwise.

    It performs this test by checking if the module is already in %INC.

  _is_class_loadable
    Provided with a package name, a.k.a. a class, and an optional version
    and this will endeavour to check if that class is installed and if a
    version is provided, if it is greater or equal to the version provided.

    If the module is not already loaded and a version was provided, it uses
    Module::Metadata to get that module version.

    It returns true if the module can be loaded or false otherwise.

    If an error occurred, it sets an error and returns "undef", so be sure
    to check whether the return value is defined.

  _is_class_loaded
    Provided with a package name, a.k.a. a class, and this returns true if
    the class has already been loaded or false otherwise.

    If you are running under mod_perl, this method will use "loaded" in
    Apache2::Module to find out, otherwise, it will simply check if the
    class exists in %INC

  _is_code
    Provided with some value, possibly, undefined, and this returns true if
    it is a "CODE", such as a subroutine reference or an anonymous
    subroutine, or false otherwise.

  _is_empty
    This checks if a value was provided, and if it is defined, or if it has
    a positive length, or is a scalar object that has the method "defined",
    which returns false.

    Based on those checks, it returns true (1) if it appears the value is
    undefined or empty, and false (0) otherwise.

  _is_glob
    Provided with some value, possibly, undefined, and this returns true if
    it is a filehandle, or false otherwise.

  _is_hash
    Same as "_is_array", but for hash reference.

  _is_integer
    Returns true if the value provided is an integer, or false otherwise. A
    valid value includes an integer starting with "+" or "-"

  _is_ip
    Returns true if the given IP has a syntax compliant with IPv4 or IPv6
    including CIDR notation or not, false otherwise.

    For this method to work, you need to have installed Regexp::Common::net

  _is_number
    Returns true if the provided value looks like a number, false otherwise.

  _is_object
    Provided with some data, this checks if the data is an object. It uses
    "blessed" in Scalar::Util to achieve that purpose.

  _is_overloaded
    Provided with some value, presumably an object, and this will return
    true if it is overloaded in some way, or false if it is not.

  _is_scalar
    Provided with some data, this checks if the data is of type scalar
    reference, e.g. "SCALAR(0x7fc0d3b7cea0)", even if it is an object.

  _is_uuid
    Provided with a non-zero length value and this will check if it looks
    like a valid "UUID", i.e. a unique universal ID, and upon successful
    validation will set the value and return its representation as a
    Module::Generic::Scalar object.

    An empty string or "undef" can be provided and will not be checked.

  _load_class
        $self->_load_class( 'My::Module' ) || die( $self->error );
        $self->_load_class( 'My::Module', qw( :some_tags SOME_CONSTANTS_TO_IMPORT ) ) || die( $self->error );
        $self->_load_class(
            'My::Module',
            qw( :some_tags SOME_CONSTANTS_TO_IMPORT ),
            { version => 'v1.2.3', caller => 'Its::Me' }
        ) || die( $self->error );
        $self->_load_class( 'My::Module', { no_import => 1 } ) || die( $self->error );

    Provided with a class/package name, some optional list of semantics to
    import, and, as the last parameter, an optional hash reference of
    options and this will attempt to load the module. This uses "use" in
    perlfunc, no external module.

    Upon success, it returns the package name loaded.

    It traps any error with an eval and return "undef" in perlfunc if an
    error occurred and sets an "error" accordingly.

    Possible options are:

    *caller*
        The package name of the caller. If this is not provided, it will
        default to the value provided with "caller" in perlfunc

    *no_import*
        Set to a true value and this will prevent the loaded module from
        importing anything into your namespace.

        This is the equivalent of doing:

            use My::Module ();

    *version*
        The minimum version for this class to load. This value is passed
        directly to "use" in perlfunc

  _load_classes
    This will load multiple classes by providing it an array reference of
    class name to load and an optional hash or hash reference of options,
    similar to those provided to "_load_class"

    If one of those classes failed to load, it will return immediately after
    setting an "error".

  _lvalue
    This provides a generic lvalue method that can be used both in assign
    context or lvalue context.

    As of version 0.29.6, this is an alias for "_set_get_callback", which
    provides more extensive features.

  _obj2h
    This ensures the module object is an hash reference, such as when the
    module object is based on a file handle for example. This permits
    Module::Generic to work no matter what is the underlying data type
    blessed into an object.

  _on_error
    Sets or gets a code reference, acting as a callback that will be
    triggered upon call to "error" or "pass_error" with an error.

        return( $self->error( "Oops" ) ) if( $something_bad_happened );
        # or
        return( $self->pass_error( $another_error_object ) ) if( $something_bad_happened );

  _parse_timestamp
    Provided with a string representing a date or datetime, and this will
    try to parse it and return a DateTime object. It will also create a
    DateTime::Format::Strptime to preserve the original date/datetime string
    representation and assign it to the DateTime object. So when the
    DateTime object is stringified, it displays the same string that was
    originally parsed.

    Supported formats are:

    "2019-10-03 19-44+0000" or "2019-10-03 19:44:01+0000"
        Found in GNU PO files for example.

    "2019-06-19 23:23:57.000000000+0900"
        Found in PostgreSQL

    "2019-06-20T11:08:27"
        Matching ISO8601 format

    "2019-06-20 02:03:14"
        Found in SQLite

    "2019-06-20 11:04:01"
        Found in MySQL

    "Sun, 06 Oct 2019 06:41:11 GMT"
        Standard HTTP dates

    "12 March 2001 17:07:30 JST"
    "12-March-2001 17:07:30 JST"
    "12/March/2001 17:07:30 JST"
    "12 March 2001 17:07"
    "12 March 2001 17:07 JST"
    "12 March 2001 17:07:30+0900"
    "12 March 2001 17:07:30 +0900"
    "Monday, 12 March 2001 17:07:30 JST"
    "Monday, 12 Mar 2001 17:07:30 JST"
    "03/Feb/1994:00:00:00 0000"
    "2019-06-20"
    "2019/06/20"
    2016.04.22
    "2014, Feb 17"
    "17 Feb, 2014"
    "February 17, 2009"
    "15 July 2021"
    22.04.2016
    "22-04-2016"
    "17. 3. 2018."
    "17.III.2020"
    "17. III. 2018."
    20030613
    "2021年7月14日"
        Japanese regular date using occidental years

    "令和3年7月14日"
        Japanese regular date using Japanese era years

    Unix timestamp possibly followed by a dot and milliseconds
    Relative date to current date and time
        Example:

            -5Y - 5 years
            +2M + 2 months
            +3D + 3 days
            -2h - 2 hours
            -4m - 4 minutes
            -10s - 10 seconds

    'now'
        The word now will set the return value to the current date and time

  _set_get
        sub name { return( shift->_set_get( 'name', @_ ) ); }

    Provided with an object property name and some value and this will set
    or get that value for that property.

    However, if the value stored is an array and is called in list context,
    it will return the array as a list and not the array reference. Same
    thing for an hash reference. It will return an hash in list context. In
    scalar context, it returns whatever the value is, such as array
    reference, hash reference or string, etc.

  _set_get_array
    Provided with an object property name and some data and this will store
    the data as an array reference.

    It returns the current value stored, such as an array reference
    notwithstanding it is called in list or scalar context.

    Example :

        sub products { return( shift->_set_get_array( 'products', @_ ) ); }

  _set_get_array_as_object
    Provided with an object property name and some data and this will store
    the data as an object of Module::Generic::Array

    If this is called with no data set, an object is created with no data
    inside and returned

    Example :

        # In your module
        sub products { return( shift->_set_get_array_as_object( 'products', @_ ) ); }

    And using your method:

        printf( "There are %d products\n", $object->products->length );
        $object->products->push( $new_product );

    Alternatively, you can pass an hash reference instead of an object
    property to provide callbacks that will be called upon addition or
    removal of value.

    This hash reference can contain the following properties:

    callbacks
        An hash reference of operation type "add" (or "set")) to callback
        subroutine name or code reference pairs.

    field
        The object property name

    wantlist
        Boolean. If true, then it will return a list in list context instead
        of the array object.

    For example:

        sub children { return( shift->set_get_array_as_object({
            field => 'children',
            callbacks => 
            {
                set => '_some_add_callback',
            },
        }), @_ ); }

    The value of the callback can be either a subroutine name or a code
    reference.

  _set_get_boolean
        sub is_true { return( shift->_set_get_boolean( 'is_true', @_ ) ); }

    Provided with an object property name and some data and this will store
    the data as a boolean value.

    If the data provided is a JSON::PP::Boolean or Module::Generic::Boolean
    object, the data is stored as is.

    If the data is a scalar reference, its referenced value is check and
    "true" in Module::Generic::Boolean or "false" in
    Module::Generic::Boolean is set accordingly.

    If the data is a string with value of "true" or "val" "true" in
    Module::Generic::Boolean or "false" in Module::Generic::Boolean is set
    accordingly.

    Otherwise the data provided is checked if it is a true value or not and
    "true" in Module::Generic::Boolean or "false" in
    Module::Generic::Boolean is set accordingly.

    If no value is provided, and the object property has already been set,
    this performs the same checks as above and returns either a
    JSON::PP::Boolean or a Module::Generic::Boolean object.

    Alternatively, you can pass an hash reference instead of an object
    property to provide callbacks that will be called upon addition or
    removal of value.

    This hash reference can contain the following properties:

    field
        The object property name

    callbacks
        An hash reference of operation type "add" (or "set") to callback
        subroutine name or code reference pairs.

    For example:

        sub is_valid { return( shift->set_get_boolean({
            field => 'is_valid',
            callbacks => 
            {
                set => '_some_add_callback',
            },
        }), @_ ); }

    The value of the callback can be either a subroutine name or a code
    reference.

  _set_get_callback
        sub name : lvalue { return( shift->_set_get_callback({
            get => sub
            {
                my $self = shift( @_ );
                # The context hash is available with $_
                if( $_->{list} )
                {
                    return( @{$self->{name}} );
                }
                else
                {
                    return( $self->{name} );
                }
            },
            set => sub
            {
                my $self = shift( @_ );
                $self->message( 1, "Got here for 'name' in setter callback" );
                return( $self->{name} = shift( @_ ) );
            },
            field => 'name'
        }, @_ ) ); }
        # ^^^^
        # Don't forget the @_ !

    Then, it can be called indifferently as:

        my $rv = $obj->name( 'John' );
        # $rv is John
        $rv = $obj->name;
        # $rv is John
        $obj->name = 'Peter';
        $rv = $obj->name;
        # $rv is Peter

        $obj->colours( qw( orange blue ) );
        my @colours = $obj->colours;
        # returns a list of colours orange and blue
        my $colour = $obj->colours;
        # $colour is 'orange'

    Given an hash reference of parameters, and this support method will call
    the accessor "get" callback or mutator "set" callback depending on
    whether any arguments were provided.

    This support method supports "lvalue" methods as described in "Lvalue
    subroutines" in perlfunc

    It is similar as Sentinel, but on steroid, since it handles exception,
    and provides context, which is often critical.

    If a fatal exception occurs in a callback, it is trapped using try-catch
    block and an error object is set and "undef" is returned.

    However if an error occurs while operating in an "lvalue" assigned
    context, such as:

        $obj->name = 'Peter';

    Then, to check if there was an error, you could do:

        if( $obj->error )
        {
            # Do something here
        }

    If the "fatal" option is set to true, then it would simply die instead.

    Supported options are:

    *   "fatal"

        Boolean. If true, this will result in any exception becoming fatal
        and thus die.

    *   "field"

        The name of the object field for which this helper method is used.
        This is optional.

    *   "get"

        The accessor subroutine reference or anonymous subroutine that will
        handle retrieving data.

        This is a mandatory option and this support method will die if this
        is not provided.

        It will be passed the current object, and return whatever is
        returned in list context, or in any other context, the first value
        that this callback would return.

        Also the special variable $_ will be available and contain the call
        context.

    *   "set"

        The mutator subroutine reference or anonymous subroutine that will
        handle storing data.

        This is an optional option. This means you can set only an accessor
        "get" callback without specifying a mutator "set" callback.

        It will be passed the current object, and the list of arguments. If
        the method is used as a regular method, as opposed to an lvalue
        subroutine, then multiple arguments may be passed:

            $obj->colours( qw( blue orange ) );

        but, if used as an "lvalue" method, of course, only one argument
        will be available:

            $obj->name = 'John';

        Also the special variable $_ will be available and contain the call
        context.

        The value returned is passed back to the caller.

    The "context" provided with the special variable $_ inside the callback
    may have the following properties:

    *   "assign"

        This is true when the call context is an "lvalue" subroutine to
        which a value is being assigned, such as:

            $obj->name = 'John';

    *   "boolean"

        This is true when the call context is a boolean, such as:

            if( $obj->active )
            {
                # Do something
            }

    *   "code"

        This is true when the call context is a code reference, such as:

            $obj->my_callback->();

    *   "count"

        Contains the number of arguments expected by the caller. This is
        especially interesting when in list context.

    *   "glob"

        This is true when the call context is a glob.

    *   "hash"

        This is true when the call context is an hash reference, such as:

            $obj->meta({ client_id => 1234567 });
            my $id = $obj->meta->{client_id};

    *   "list"

        This is true when the call context is a list, such as:

            my @colours = $obj->colours;

    *   "lvalue"

        This is true when the call context is an "lvalue" subroutine, such
        as:

            $obj->name = 'John';

    *   "object"

        This is true when the call context is an object, such as:

            $obj->something->another_method();

    *   "refscalar"

            my $name = ${$obj->name};

    *   "rvalue"

        This is true when the call context is from the right-hand side.

            my $name = $obj->name;

    *   "scalar"

        This is true when the call context is a scalar:

            my $name = $obj->name;
            say $name; # John

    *   "void"

        This is true when the call context is void, such as:

            $obj->pointless();

    See also Want for more on this context-rich information.

  _set_get_class
    Given an object property name, a dynamic class fiels definition hash
    (dictionary), and optional arguments, this special method will create
    perl packages on the fly by calling the support method "__create_class"

    For example, consider the following:

        #!/usr/local/bin/perl
        BEGIN
        {
            use strict;
            use Data::Dumper;
        };

        {
            my $o = MyClass->new( debug => 3 );
            $o->setup->age( 42 );
            print( "Age is: ", $o->setup->age, "\n" );
            print( "Setup object is: ", $o->setup, "\n" );
            $o->setup->billing->interval( 'month' );
            print( "Billing interval is: ", $o->setup->billing->interval, "\n" );
            print( "Billing object is: ", $o->setup->billing, "\n" );
            $o->setup->rgb( 255, 122, 100 );
            print( "rgb: ", join( ', ', @{$o->setup->rgb} ), "\n" );
            exit( 0 );
        }

        package MyClass;
        BEGIN
        {
            use strict;
            use lib './lib';
            use parent qw( Module::Generic );
        };

        sub setup 
        {
            return( shift->_set_get_class( 'setup',
            {
            name => { type => 'scalar' },
            # or being lazy:
            # name => 'scalar',
            age => { type => 'number' },
            metadata => { type => 'hash' },
            rgb => { type => 'array' },
            url => { type => 'uri' },
            online => { type => 'boolean' },
            created => { type => 'datetime' },
            billing => { type => 'class', definition =>
                {
                interval => { type => 'scalar' },
                frequency => { type => 'number' },
                nickname => { type => 'scalar' },
                }}
            }) );
        }

        1;

        __END__

    This will yield:

        Age is: 42
        Setup object is: MyClass::Setup=HASH(0x7fa805abcb20)
        Billing interval is: month
        Billing object is: MyClass::Setup::Billing=HASH(0x7fa804ec3f40)
        rgb: 255, 122, 100

    The advantage of this over _set_get_hash_as_object is that here one
    controls what fields / method are supported and with which data type.

  _set_get_class_array
    Provided with an object property name, a dictionary to create a dynamic
    class with "__create_class" and an array reference of hash references
    and this will create an array of object, each one matching a set of data
    provided in the array reference. So for example, imagine you had a
    method such as below in your module :

        sub products { return( shift->_set_get_class_array( 'products', 
        {
        name        => { type => 'scalar' },
        customer    => { type => 'object', class => 'My::Customer' },
        orders      => { type => 'array_as_object' },
        active      => { type => 'boolean' },
        created     => { type => 'datetime' },
        metadata    => { type => 'hash' },
        stock       => { type => 'number' },
        url         => { type => 'uri' },
        }, @_ ) ); }

    Then your script would call this method like this :

        $object->products([
        { name => 'Cool product', customer => { first_name => 'John', last_name => 'Doe', email => 'john.doe@example.com' }, active => 1, stock => 10, created => '2020-04-12T07:10:30' },
        { name => 'Awesome tool', customer => { first_name => 'Mary', last_name => 'Donald', email => 'm.donald@example.com' }, active => 1, stock => 15, created => '2020-05-12T15:20:10' },
        ]);

    And this would store an array reference containing 2 objects with the
    above data.

  _set_get_class_array_object
    Same as "=head2 _set_get_class_array", but this returns an array object
    instead of just a perl array.

    When called in list context, it will return its values as a list,
    otherwise it will return an array object

  _set_get_code
    Provided with an object property name and some code reference and this
    stores and retrieve the current value.

    It returns under and set an error if the provided value is not a code
    reference.

  _set_get_datetime
        sub created_on { return( shift->_set_get_datetime( 'created_on', @_ ) ); }

    Provided with an object property name and asome date or datetime string
    and this will attempt to parse it and save it as a DateTime object.

    If the data is a 10 digits integer, this will treat it as a unix
    timestamp.

    Parsing also recognise special word such as "now"

    The created DateTime object is associated a DateTime::Format::Strptime
    object which enables the DateTime object to be stringified as a unix
    timestamp using local time stamp, whatever it is.

    Even if there is no value set, and this method is called in chain, it
    returns a Module::Generic::Null whose purpose is to enable chaining
    without doing anything meaningful. For example, assuming the property
    *created* of your object is not set yet, but in your script you call it
    like this:

        $object->created->iso8601

    Of course, the value of "iso8601" will be empty since this is a fake
    method produced by Module::Generic::Null. The return value of a method
    should always be checked.

  _set_get_file
        sub file { return( shift->_set_get_file( 'file', @_ ) ); }

    Provided with an object property name and a file and this will store the
    given file as a Module::Generic::File object.

    It returns "undef" and set an error if the provided value is not a
    proper file.

    Note that the files does not need to exist and it can also be a
    directory or a symbolic link or any other file on the system.

  _set_get_glob
        sub handle { return( shift->_set_get_glob( 'handle', @_ ) ); }

    Provided with an object property name and a glob (file handle) and this
    will store the given glob.

    It returns "undef" and set an error if the provided value is not a glob.

  _set_get_hash
        sub metadata { return( shift->_set_get_hash( 'metadata', @_ ) ); }

    Provided with an object property name and an hash reference and this set
    the property name with this hash reference.

    You can even pass it an associative array, and it will be saved as a
    hash reference, such as :

        $object->metadata(
            transaction_id => 123,
            customer_id => 456
        );

        my $hash = $object->metadata;

  _set_get_hash_as_mix_object
        sub metadata { return( shift->_set_get_hash_as_mix_object( 'metadata', @_ ) ); }

    Provided with an object property name, and an optional hash reference
    and this returns a Module::Generic::Hash object, which allows to
    manipulate the hash just like any regular hash, but it provides on top
    object oriented method described in details in Module::Generic::Hash.

    This is different from "_set_get_hash_as_object" below whose keys and
    values are accessed as dynamic methods and method arguments.

  _set_get_hash_as_object
    Provided with an object property name, an optional class name and an
    hash reference and this does the same as in "_set_get_hash", except it
    will create a class/package dynamically with a method for each of the
    hash keys, so that you can call the hash keys as method.

    Also it does this recursively while handling looping, in which case, it
    will reuse the object previously created, and also it takes care of
    adapting the hash key to a proper field name, so something like
    "99more-options" would become "more_options". If the value itself is a
    hash, it processes it recursively transforming "99more-options" to a
    proper package name "MoreOptions" prepended by $class_name provided as
    argument or whatever upper package was used in recursion processing.

    For example in your module :

        sub metadata { return( shift->_set_get_hash_as_object( 'metadata', @_ ) ); }

    Then populating the data :

        $object->metadata({
            first_name => 'John',
            last_name => 'Doe',
            email => 'john.doe@example.com',
        });

        printf( "Customer name is %s\n", $object->metadata->last_name );

  _set_get_ip
        sub ip { return( shift->_set_get_ip( 'ip', @_ ) ); }

    This helper method takes a value and check if it is a valid IP address
    using "_is_ip". If "undef" or zero-byte value is provided, it will
    merely accept it, as it can be used to reset the value by the caller.

    If a value is successfully set, it returns a Module::Generic::Scalar
    object representing the string passed.

    From there you can pass the result to Net::IP in your own code, assuming
    you have that module installed.

  _set_get_lvalue
    This is now an alias for "_set_get_callback"

  _set_get_number
    Provided with an object property name and a number, and this will create
    a Module::Generic::Number object and return it.

    As of version v0.13.0 it also works as a lvalue method. See perlsub

    In your module:

        package MyObject;
        use parent qw( Module::Generic );
    
        sub level : lvalue { return( shift->_set_get_number( 'level', @_ ) ); }

    In the script using module "MyObject":

        my $obj = MyObject->new;
        $obj->level = 3; # level is now 3
        # or
        $obj->level( 4 ) # level is now 4
        print( "Level is: ", $obj->level, "\n" ); # Level is 4
        print( "Is it an odd number: ", $obj->level->is_odd ? 'yes' : 'no', "\n" );
        # Is it an od number: no
        $obj->level++; # level is now 5

    Alternatively, you can pass an hash reference instead of an object
    property to provide callbacks that will be called upon addition or
    removal of value.

    This hash reference can contain the following properties:

    *   "callbacks"

        An hash reference of operation type "add" (or "set") to callback
        subroutine name or code reference pairs.

    *   "field"

        The object property name

    *   "undef_ok"

        If this is set to a true value, this support method will allow undef
        to be set. Default to false, which means an undefined value passed
        will be ignored.

    For example:

        sub length { return( shift->set_get_number({
            field => 'length',
            callbacks => 
            {
                set => '_some_add_callback',
            },
        }), @_ ); }

    The value of the callback can be either a subroutine name or a code
    reference.

  _set_get_number_or_object
    Provided with an object property name and a number or an object and this
    call the value using "_set_get_number" or "_set_get_object" respectively

  _set_get_object
        sub myobject { return( shift->_set_get_object({ field => 'myobject', no_init => 1 }, My::Class, @_ ) ); }

        sub myobject { return( shift->_set_get_object({
            field => 'myobject',
            no_init => 1,
            callback => sub
            {
                my( $class, $args ) = @_;
                return( $class->new( $args->[0] ) );
            },
        }, My::Class, @_ ) ); }

        sub myobject { return( shift->_set_get_object( 'myobject', My::Class, @_ ) ); }

    Provided with an object property name, a class/package name and some
    data and this will initiate a new object of the given class passing it
    the data.

    The property name can also be an hash reference that will be used to
    provide more granular settings:

    *   "callback"

        A callback code reference that will be passed the module class name
        and the arguments as an array reference.

        This is used to instantiate the module object in a particular way
        and/or to have finer control about object instantiation.

        Any fatal error during object instantiation is caught and an error
        would be set and "undef" would be returned in scalar context, or an
        empty list in list context.

    *   "field"

        The actual property name

    *   "no_init"

        Boolean that, when set, instruct to not instantiate a class object
        if one is not instantiated yet.

    If you pass an undefined value, it will set the property as undefined,
    removing whatever was set before.

    You can also provide an existing object of the given class.
    "_set_get_object" will check the object provided does belong to the
    specified class or it will set an error and return undef.

    It returns the object currently set, if any.

  _set_get_object_lvalue
    Same as "_set_get_object_without_init" but with the possibility of
    setting the object value as an lvalue method:

        $o->my_property = $my_object;

  _set_get_object_without_init
        sub mymethod { return( shift->_set_get_object_without_init( 'mymethod', 'Some::Module', @_ ) ); }
        # or
        sub mymethod { return( shift->_set_get_object_without_init({
            field => 'mymethod',
            callback => sub
            {
                my( $class, $args ) = @_;
                return( $class->new( $args->[0] ) );
            },
        }, 'Some::Module', @_ ) ); }
        # then
        my $this = $obj->mymethod; # possibly undef if it was never instantiated
        # return the C<Some::Module> object after having instantiated it
        my $this = $obj->mymethod( some => parameters );

    Sets or gets an object, but contrary to "_set_get_object" this method
    will not try to instantiate the object, unless of course you pass it
    some values.

    Alternatively, you can pass an hash reference, instead of the object
    property name, with the following properties:

    *   "field"

        Mandatory. The object property name.

    *   "callback"

        Optional. A code reference like an anonymous subroutine that will be
        called with the class and an array reference of values provided, but
        possibly empty.

        Whatever this returns will set the value for this object property.

    This is a useful callback when the module instantiation either does not
    use the "new" method or does not simply take one or multiple arguments,
    such as when the instantiation method would require an hash of
    parameters, such as Email::Address::XS

  _set_get_object_array2
        sub mymethod { return( shift->_set_get_object_array2( 'mymethod', 'Some::Module', @_ ) ); }
        # or
        sub mymethod { return( shift->_set_get_object_array2({
            field => 'mymethod',
            callback => sub
            {
                my( $class, $args ) = @_;
                return( $class->new( $args->[0] ) );
            },
        }, 'Some::Module', @_ ) ); }

    Provided with an object property name, a class/package name and some
    array reference itself containing array references each containing hash
    references or objects, and this will create an array of array of
    objects.

    Alternatively, you can pass an hash reference, instead of the object
    property name, with the following properties:

    *   "field"

        Mandatory. The object property name.

    *   "callback"

        Optional. A code reference like an anonymous subroutine that will be
        called with the class and an array reference of values provided, but
        possibly empty.

    This is a useful callback when the module instantiation either does not
    use the "new" method or does not simply take one or multiple arguments,
    such as when the instantiation method would require an hash of
    parameters, such as Email::Address::XS

  _set_get_object_array
        sub mymethod { return( shift->_set_get_object_array( 'mymethod', 'Some::Module', @_ ) ); }
        # or
        sub mymethod { return( shift->_set_get_object_array({
            field => 'mymethod',
            callback => sub
            {
                my( $class, $args ) = @_;
                return( $class->new( $args->[0] ) );
            },
        }, 'Some::Module', @_ ) ); }

    Provided with an object property name and a class/package name and
    similar to "_set_get_object_array2" this will create an array reference
    of objects.

    Alternatively, you can pass an hash reference, instead of the object
    property name, with the following properties:

    *   "field"

        Mandatory. The object property name.

    *   "callback"

        Optional. A code reference like an anonymous subroutine that will be
        called with the class and an array reference of values provided, but
        possibly empty.

    This is a useful callback when the module instantiation either does not
    use the "new" method or does not simply take one or multiple arguments,
    such as when the instantiation method would require an hash of
    parameters, such as Email::Address::XS

        sub emails { return( shift->_set_get_object_array({
            field => 'emails',
            callback => sub
            {
                my( $class, $args ) = @_;
                return( $class->parse_bare_address( $args->[0] ) );
            },
        }, 'Email::Address::XS', @_ ) ); }

  _set_get_object_array_object
    Provided with an object property name, a class/package name and some
    data and this will create an array of object similar to
    "_set_get_object_array", except the array produced is a
    Module::Generic::Array

    This method accepts the same arguments as "_set_get_object_array"

  _set_get_object_variant
    Provided with an object property name, a class/package name and some
    data, and depending whether the data provided is an hash reference or an
    array reference, this will either instantiate an object for the given
    hash reference or an array of objects with the hash references in the
    given array.

    This means the value stored for the object property will vary between an
    hash or array reference.

    Alternatively, you can pass an hash reference, instead of the object
    property name, with the following properties:

    *   "field"

        Mandatory. The object property name.

    *   "callback"

        Optional. A code reference like an anonymous subroutine that will be
        called with the class and an array reference of values provided, but
        possibly empty.

    This is a useful callback when the module instantiation either does not
    use the "new" method or does not simply take one or multiple arguments,
    such as when the instantiation method would require an hash of
    parameters, such as Email::Address::XS

        sub emails { return( shift->_set_get_object_variant({
            field => 'emails',
            callback => sub
            {
                my( $class, $args ) = @_;
                return( $class->parse_bare_address( $args->[0] ) );
            },
        }, 'Email::Address::XS', @_ ) ); }

  _set_get_scalar
        sub name { return( shift->_set_get_scalar( 'name', @_ ) ); }

    Provided with an object property name, and a string, possibly a number
    or anything really and this will set the property value accordingly.
    Very straightforward.

    It returns the currently value stored.

  _set_get_scalar_as_object
    Provided with an object property name, and a string or a scalar
    reference and this stores it as an object of Module::Generic::Scalar

    If there is already an object set for this property, the value provided
    will be assigned to it using "set" in Module::Generic::Scalar

    If it is called and not value is set yet, this will instantiate a
    Module::Generic::Scalar object with no value.

    So a call to this method can safely be chained to access the
    Module::Generic::Scalar methods. For example :

        sub name { return( shift->_set_get_scalar_as_object( 'name', @_ ) ); }

    Then, calling it :

        $object->name( 'John Doe' );

    Getting the value :

        my $cust_name = $object->name;
        print( "Nothing set yet.\n" ) if( !$cust_name->length );

    Alternatively, you can pass an hash reference instead of an object
    property to provide callbacks that will be called upon addition or
    removal of value.

    This hash reference can contain the following properties:

    field
        The object property name

    callbacks
        An hash reference of operation type "add" (or "set") to callback
        subroutine name or code reference pairs.

    For example:

        sub name { return( shift->set_get_scalar_as_object({
            field => 'name',
            callbacks => 
            {
                set => '_some_add_callback',
            },
        }), @_ ); }

    The value of the callback can be either a subroutine name or a code
    reference.

  _set_get_scalar_or_object
    Provided with an object property name, and a class/package name and this
    stores the value as an object calling "_set_get_object" if the value is
    an object of class *class* or as a string calling "_set_get_scalar"

    If no value has been set yet, this returns a Module::Generic::Null
    object to enable chaining.

  _set_get_uri
        sub uri { return( shift->_set_get_uri( 'uri', @_ ) ); }
        sub uri { return( shift->_set_get_uri( { field => 'uri', class => 'URI::Fast' }, @_ ) ); }

    Provided with an object property name, and an uri and this creates an
    URI object and sets the property value accordingly.

    Alternatively, the property name can be an hash with the following
    properties:

    *field*
        The object property name

    *class*
        The URI class to use. By default, URI, but you could also use
        URI::Fast, or other class of your choice. That class will be loaded,
        if it is not loaded already.

    It accepts an URI object (or any other URI class object), an uri or urn
    string, or an absolute path, i.e. a string starting with "/".

    It returns the current value, if any, so the return value could be
    undef, thus it cannot be chained. Maybe it should return a
    Module::Generic::Null object ?

  _set_get_uuid
    Provided with an object, a property name, and an UUID (Universal Unique
    Identifier) and this stores it as an object of Module::Generic::Scalar.

    If an empty or undefined value is provided, it will be stored as is.

    However, if there is no value and this method is called in object
    context, such as in chaining, this will return a special
    Module::Generic::Null object that prevents perl error that whatever
    method follows was called on an undefined value.

  _set_get_version
        sub version { return( shift->_set_get_version( 'version', @_ ) ); }
        # or
        sub version : lvalue { return( shift->_set_get_version( 'version', @_ ) ); }
        # or
        sub version : lvalue { return( shift->_set_get_version( { field => 'version', class => 'Perl::Version' }, @_ ) ); }

    Provided with an object, a property name, and a version string and this
    stores it as an object of version by default.

    Alternatively, the property name can be an hash with the following
    properties:

    *field*
        The object property name

    *class*
        The version class to use. By default, version, but you could also
        use Perl::Version, or other class of your choice. That class will be
        loaded, if it is not loaded already.

    The value can also be assigned as an lvalue. Assuming you have a method
    "version" that implements "_set_get_version":

        $obj->version = $version;

    would work, but of course also:

        $obj->version( $version );

    The value can be a legitimate version string, or a version object
    matching the "class" to be used, which is by default version. If it is a
    string, it will be made an object of the class specified using "parse"
    if that class supports it, or by simply calling "new".

    When called in get mode, it will convert any value pre-set, if any, into
    a version object of the specified class if the value is not an object of
    that class already, and return it, or else it will return an empty
    string or undef whatever you will have set in your object for this
    property.

  _to_array_object
    Provided with arguments or not, and this will return a
    Module::Generic::Array object of those data.

        my $array = $self->_to_array_object( qw( Hello world ) ); # Becomes an array object of 'Hello' and 'world'
        my $array = $self->_to_array_object( [qw( Hello world )] ); # Becomes an array object of 'Hello' and 'world'

  _warnings_is_enabled
    Called with the class object or providing another class object as
    argument, and this returns true if warnings are enabled for the given
    class, false otherwise.

    Example:

        $self->_warnings_is_enabled();
        # Providing another class object
        $self->_warnings_is_enabled( $other_object );

  _warnings_is_registered
    Called with the class object or providing another class object as
    argument, and this returns true if warnings are registered for the given
    class, false otherwise.

    This is useful, because calling "warnings::enabled()" to check if
    warnings are enabled for a given class when that class has not
    registered for warnings using the pragma "use warnings::register" will
    produce an error "Unknown warnings category".

    Example:

        $self->_warnings_is_registered();
        # Providing another class object
        $self->_warnings_is_registered( $other_object );

  __dbh
    if your module has the global variables "DB_DSN", this will create a
    database handler using DBI

    It will also use the following global variables in your module to set
    the database object: "DB_RAISE_ERROR", "DB_AUTO_COMMIT",
    "DB_PRINT_ERROR", "DB_SHOW_ERROR_STATEMENT", "DB_CLIENT_ENCODING",
    "DB_SERVER_PREPARE"

    If "DB_SERVER_PREPARE" is provided and true, "pg_server_prepare" will be
    set to true in the database handler.

    It returns the database handler object.

  DEBUG
    Return the value of your global variable *DEBUG*, if any.

  VERBOSE
    Return the value of your global variable *VERBOSE*, if any.

ERROR & EXCEPTION HANDLING
    This module has been developed on the idea that only the main part of
    the application should control the flow and trigger exit. Thus, this
    module and all the others in this distribution do not die, but rather
    set and error and return undef. So you should always check for the
    return value.

    Error triggered are transformed into an Module::Generic::Exception
    object, or any exception class that is specified by the object property
    "_exception_class". For example:

        sub init
        {
            my $self = shift( @_ );
            $self->SUPER::init( @_ ) || return( $self->pass_error );
            $self->{_exception_class} = 'My::Exception';
            return( $self );
        }

    Those error objects can then be retrieved by calling "error"

    If, however, you wanted errors triggered to be fatal, you can set the
    object property "fatal" to a true value and/or set your package global
    variable $FATAL_ERROR to true. When "error" is called with an error, it
    will "die" in perlfunc with the error object rather than merely
    returning "undef". For example:

        package My::Module;
        BEGIN
        {
            use strict;
            use warnings;
            use parent qw( Module::Generic );
            our $VERSION = 'v0.1.0';
            our $FATAL_ERROR = 1;
        };

        sub init
        {
            my $self = shift( @_ );
            $self->{fatal} = 1;
            $self->SUPER::init( @_ ) || return( $self->pass_error );
            $self->{_exception_class} = 'My::Exception';
            return( $self );
        }

    To catch fatal error you can use a "try-catch" block such as implemented
    by Nice::Try.

    Since perl version 5.33.7
    <https://perldoc.perl.org/blead/perlsyn#Try-Catch-Exception-Handling>
    you can use the try-catch block using an experimental feature "use
    feature 'try';", but this does not support "catch" by exception class.

SERIALISATION
    The modules in the Module::Generic distribution all supports
    Storable::Improved (or the legacy Storable), Sereal and CBOR
    serialisation, by implementing the methods "FREEZE", "THAW",
    "STORABLE_freeze", "STORABLE_thaw"

    Even the IO modules like Module::Generic::File::IO and
    Module::Generic::Scalar::IO can be serialised and deserialised if the
    methods "FREEZE" and "THAW" are used. By design the methods
    "STORABLE_freeze" and "STORABLE_thaw" are not implemented in those
    modules because it would trigger a Storable exception "Unexpected object
    type (8) in store_hook()". Instead it is strongly encouraged you use the
    improved Storable::Improved which addresses and mitigate those issues.

    For serialisation with Sereal, make sure to instantiate the Sereal
    encoder with the "freeze_callbacks" option set to true, otherwise,
    "Sereal" will not use the "FREEZE" and "THAW" methods.

    See "FREEZE/THAW CALLBACK MECHANISM" in Sereal::Encoder for more
    information.

    For CBOR, it is recommended to use the option "allow_sharing" to enable
    the reuse of references, such as:

        my $cbor = CBOR::XS->new->allow_sharing;

    Also, if you use the option "allow_tags" with JSON, then all of those
    modules will work too, since this option enables support for the
    "FREEZE" and "THAW" methods.

SEE ALSO
    Module::Generic::Exception, Module::Generic::Array,
    Module::Generic::Scalar, Module::Generic::Boolean,
    Module::Generic::Number, Module::Generic::Null, Module::Generic::Dynamic
    and Module::Generic::Tie, Module::Generic::File, Module::Generic::Finfo,
    Module::Generic::SharedMem, Module::Generic::Scalar::IO

    Number::Format, Class::Load, Scalar::Util

AUTHOR
    Jacques Deguest <jack@deguest.jp>

COPYRIGHT & LICENSE
    Copyright (c) 2000-2020 DEGUEST Pte. Ltd.

    You can use, copy, modify and redistribute this package and associated
    files under the same terms as Perl itself.

