NAME
    MooseX::Types::Structured - Structured Type Constraints for Moose

SYNOPSIS
    The following is example usage for this module.

        package MyApp::MyClass;
            
    use Moose;
        use MooseX::Types::Moose qw(Str Int);
        use MooseX::Types::Structured qw(Dict Tuple);

        has name => (isa=>Dict[first_name=>Str, last_name=>Str]);

    Then you can instantiate this class with something like:

        my $instance = MyApp::MyClass->new(
            name => {
                first_name=>'John', 
                last_name=>'Napiorkowski',
            },
        );

    But all of these would cause a constraint error for the 'name'
    attribute:

        MyApp::MyClass->new( name=>'John' );
        MyApp::MyClass->new( name=>{first_name=>'John'} );
        MyApp::MyClass->new( name=>{first_name=>'John', age=>39} );

    Please see the test cases for more examples.

DESCRIPTION
    A structured type constraint is a standard container "Moose" type
    constraint, such as an arrayref or hashref, which has been enhanced to
    allow you to explicitly name all the allow type constraints inside the
    structure. The generalized form is:

        TypeConstraint[TypeParameters]

    Where 'TypeParameters' is an array or hash of
    "Moose::Meta::TypeConstraint" type constraints.

    This type library enables structured type constraints. It is build on
    top of the MooseX::Types library system, so you should review the
    documentation for that if you are not familiar with it.

  Comparing Parameterized types to Structured types
    Parameterized constraints are built into the core Moose types 'HashRef'
    and 'ArrayRef'. Structured types have similar functionality, so their
    syntax is likewise similar. For example, you could define a
    parameterized constraint like:

        subtype ArrayOfInts,
         as Arrayref[Int];

    which would constraint a value to something like [1,2,3,...] and so on.
    On the other hand, a structured type constraint explicitly names all
    it's allowed type parameter constraints. For the example:

        subtype StringFollowedByInt,
         as Tuple[Str,Int];

    would constrain it's value to something like ['hello', 111] but
    ['hello', 'world'] would fail, as well as ['hello', 111, 'world'] and so
    on.

    Structured Constraints are not limited to arrays. You can define a
    structure against a hashref with 'Dict' as in this example:

        subtype FirstNameLastName,
         as Dict[firste=>Str, lastname=>Str];

    This would constrain a hashref to something like:

        {firstname=>'Vanessa', lastname=>'Li'};

    but all the following would fail validation:

         {first=>'Vanessa', last=>'Li'};
         {firstname=>'Vanessa', lastname=>'Li', middlename=>'NA'};   
         ['Vanessa', 'Li'];

    These structures can be as simple or elaborate as you wish. You can even
    combine various structured, parameterized and simple constraints all
    together:

        subtype crazy,
         as Tuple[
            Int,
            Dict[name=>Str, age=>Int],
            ArrayRef[Int]
         ];

    Which would match "[1, {name=>'John', age=>25},[10,11,12]]". Please
    notice how the type parameters can be visually arranged to your liking
    and to improve the clarity of your meaning. You don't need to run then
    altogether onto a single line.

  Alternatives
    You should exercise some care as to whether or not your complex
    structured constraints would be better off contained by a real object as
    in the following example:

        package MyApp::MyStruct;
        use Moose;
        
    has $_ for qw(name age);
        
    package MyApp::MyClass;
        use Moose;
        
    has person => (isa=>'MyApp::MyStruct');             
        
    my $instance = MyApp::MyClass->new(
            person=>MyApp::MyStruct->new(name=>'John', age=>39),
        );

    This method may take some additional time to setup but will give you
    more flexibility. However, structured constraints are highly compatible
    with this method, granting some interesting possibilities for coercion.
    Try:

        subtype 'MyStruct',
         as 'MyApp::MyStruct';
        
    coerce 'MyStruct',
         from (Dict[name=>Str, age=>Int]),
         via { MyApp::MyStruct->new(%$_) },
         from (Dict[last_name=>Str, first_name=>Str, dob=>DateTime]),
         via {
            my $name = $_->{first_name} .' '. $_->{last_name};
            my $age = DateTime->now - $_->{dob};
            MyApp::MyStruct->new( name=>$name, age=>$age->years );
         };

  Subtyping a structured subtype
    You need to exercise some care when you try to subtype a structured type
    as in this example:

        subtype Person,
         as Dict[name=>Str, age=>Int];
             
    subtype FriendlyPerson,
         as Person[name=>Str, age=>Int, totalFriends=>Int];

    This will actually work BUT you have to take care that the subtype has a
    structure that does not contradict the structure of it's parent. For now
    the above works, but I will clarify the syntax for this at a future
    point, so it's recommended to avoid (should not realy be needed so much
    anyway). For now this is supported in an EXPERIMENTAL way. Your
    thoughts, test cases and patches are welcomed for discussion.

  Coercions
    Coercions currently work for 'one level' deep. That is you can do:

        subtype Person,
         as Dict[name=>Str, age=>Int];
        
    subtype Fullname,
         as Dict[first=>Str, last=>Str];
        
    coerce Person,
         ## Coerce an object of a particular class
         from BlessedPersonObject,
         via { +{name=>$_->name, age=>$_->age} },
         ## Coerce from [$name, $age]
         from ArrayRef,
         via { +{name=>$_->[0], age=>$_->[1] },
         ## Coerce from {fullname=>{first=>...,last=>...}, dob=>$DateTimeObject}
         from Dict[fullname=>Fullname, dob=>DateTime],
         via {
            my $age = $_->dob - DateTime->now;
            +{
                name=> $_->{fullname}->{first} .' '. $_->{fullname}->{last},
                age=>$age->years
            }
         };

    And that should just work as expected. However, if there are any 'inner'
    coercions, such as a coercion on 'Fullname' or on 'DateTime', that
    coercion won't currently get activated.

    Please see the test '07-coerce.t' for a more detailed example.

TYPE CONSTRAINTS
    This type library defines the following constraints.

  Tuple[@constraints]
    This defines an arrayref based constraint which allows you to validate a
    specific list of constraints. For example:

        Tuple[Int,Str]; ## Validates [1,'hello']
        Tuple[Str|Object, Int]; ##Validates ['hello', 1] or [$object, 2]

  Dict [%constraints]
    This defines a hashref based constraint which allowed you to validate a
    specific hashref. For example:

        Dict[name=>Str, age=>Int]; ## Validates {name=>'John', age=>39}

EXAMPLES
    Here are some additional example usage for structured types. All
    examples can be found also in the 't/examples.t' test. Your
    contributions are also welcomed.

  Normalize a HashRef
    You need a hashref to conform to a canonical structure but are required
    accept a bunch of different incoming structures. You can normalize using
    the Dict type constraint and coercions. This example also shows
    structured types mixed which other MooseX::Types libraries.

        package Test::MooseX::Meta::TypeConstraint::Structured::Examples::Normalize;
        
    use Moose;
        use DateTime;
        
    use MooseX::Types::Structured qw(Dict Tuple);
        use MooseX::Types::DateTime qw(DateTime);
        use MooseX::Types::Moose qw(Int Str Object);
        use MooseX::Types -declare => [qw(Name Age Person)];
         
    subtype Person,
         as Dict[name=>Str, age=>Int];
        
    coerce Person,
         from Dict[first=>Str, last=>Str, years=>Int],
         via { +{
            name => "$_->{first} $_->{last}",
            age=>$_->{years},
         }},
         from Dict[fullname=>Dict[last=>Str, first=>Str], dob=>DateTime],
         via { +{
            name => "$_->{fullname}{first} $_->{fullname}{last}",
            age => ($_->{dob} - 'DateTime'->now)->years,
         }};
         
    has person => (is=>'rw', isa=>Person, coerce=>1);

SEE ALSO
    The following modules or resources may be of interest.

    Moose, MooseX::TypeLibrary, Moose::Meta::TypeConstraint,
    MooseX::Meta::TypeConstraint::Structured

TODO
    Need to clarify deep coercions, need to clarify subtypes of subtypes.

AUTHOR
    John Napiorkowski, "<jjnapiork@cpan.org>"

COPYRIGHT & LICENSE
    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

