[gitmo/MooseX-Types-Structured.git] / lib / MooseX / Types / Structured.pm

package MooseX::Types::Structured;

use 5.008;
use Moose;
use Moose::Util::TypeConstraints;
use MooseX::Meta::TypeConstraint::Structured;
use MooseX::Types -declare => [qw(Dict Tuple)];

our $VERSION = '0.04';
our $AUTHORITY = 'cpan:JJNAPIORK';

=head1 NAME

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

=head1 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 an error:

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

Please see the test cases for more examples.

=head1 DESCRIPTION

A structured type constraint is a standard container L</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 a list of type constraints.

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

=head2 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 HashOfInts,
     as Hashref[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']

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.

=head2 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 );
     };
         
=head2 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=>iIt];
         
    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.

=head2 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,
     from BlessedPersonObject,
     via { +{name=>$_->name, age=>$_->age} },
     from ArrayRef,
     via { +{name=>$_->[0], age=>$_->[1] },
     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.

=head1 TYPE CONSTRAINTS

This type library defines the following constraints.

=head2 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]

=head2 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}

=head1 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.

=head2 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);

=cut

Moose::Util::TypeConstraints::get_type_constraint_registry->add_type_constraint(
        MooseX::Meta::TypeConstraint::Structured->new(
                name => "MooseX::Types::Structured::Tuple" ,
                parent => find_type_constraint('ArrayRef'),
                constraint_generator=> sub {
                        ## Get the constraints and values to check
                        my @type_constraints = @{shift @_};            
                        my @values = @{shift @_};
                        ## Perform the checking
                        while(@type_constraints) {
                                my $type_constraint = shift @type_constraints;
                                if(@values) {
                                        my $value = shift @values;
                                        unless($type_constraint->check($value)) {
                                                return;
                                        }                               
                                } else {
                                        return;
                                }
                        }
                        ## Make sure there are no leftovers.
                        if(@values) {
                                return;
                        } elsif(@type_constraints) {
                                return;
                        }else {
                                return 1;
                        }
                }
        )
);
        
Moose::Util::TypeConstraints::get_type_constraint_registry->add_type_constraint(
        MooseX::Meta::TypeConstraint::Structured->new(
                name => "MooseX::Types::Structured::Dict",
                parent => find_type_constraint('HashRef'),
                constraint_generator=> sub {
                        ## Get the constraints and values to check
                        my %type_constraints = @{shift @_};            
                        my %values = %{shift @_};
                        ## Perform the checking
                        while(%type_constraints) {
                                my($key, $type_constraint) = each %type_constraints;
                                delete $type_constraints{$key};
                                if(exists $values{$key}) {
                                        my $value = $values{$key};
                                        delete $values{$key};
                                        unless($type_constraint->check($value)) {
                                                return;
                                        }
                                } else {
                                        return;
                                }
                        }
                        ## Make sure there are no leftovers.
                        if(%values) {
                                return;
                        } elsif(%type_constraints) {
                                return;
                        }else {
                                return 1;
                        }
                },
        )
);

=head1 SEE ALSO

The following modules or resources may be of interest.

L<Moose>, L<MooseX::TypeLibrary>, L<Moose::Meta::TypeConstraint>,
L<MooseX::Meta::TypeConstraint::Structured>

=head1 TODO

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

=head1 AUTHOR

John Napiorkowski, C<< <jjnapiork@cpan.org> >>

=head1 COPYRIGHT & LICENSE

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

=cut
        
1;