NAME

       Type::Tiny::Duck - type constraints based on the "can" method

SYNOPSIS

       Using via Types::Standard:

         package Logger {
           use Moo;
           use Types::Standard qw( HasMethods Bool );

           has debugging => ( is => 'rw', isa => Bool, default => 0 );
           has output    => ( is => 'ro', isa => HasMethods[ 'print' ] );

           sub warn {
             my ( $self, $message ) = @_;
             $self->output->print( "[WARNING] $message\n" );
           }

           sub debug {
             my ( $self, $message ) = @_;
             $self->output->print( "[DEBUG] $message\n" ) if $self->debugging;
           }
         }

       Using Type::Tiny::Duck's export feature:

         package Logger {
           use Moo;
           use Types::Standard qw( Bool );
           use Type::Tiny::Duck Printable => [ 'print' ];

           has debugging => ( is => 'rw', isa => Bool, default => 0 );
           has output    => ( is => 'ro', isa => Printable );

           sub warn {
             my ( $self, $message ) = @_;
             $self->output->print( "[WARNING] $message\n" );
           }

           sub debug {
             my ( $self, $message ) = @_;
             $self->output->print( "[DEBUG] $message\n" ) if $self->debugging;
           }
         }

       Using Type::Tiny::Duck's object-oriented interface:

         package Logger {
           use Moo;
           use Types::Standard qw( Bool );
           use Type::Tiny::Duck;

           my $Printable = Type::Type::Duck->new(
             name    => 'Printable',
             methods => [ 'print' ],
           );

           has debugging => ( is => 'rw', isa => Bool, default => 0 );
           has output    => ( is => 'ro', isa => $Printable );

           sub warn {
             my ( $self, $message ) = @_;
             $self->output->print( "[WARNING] $message\n" );
           }

           sub debug {
             my ( $self, $message ) = @_;
             $self->output->print( "[DEBUG] $message\n" ) if $self->debugging;
           }
         }

STATUS

       This module is covered by the Type-Tiny stability policy.

DESCRIPTION

       Type constraints of the general form "{ $_->can("method") }".

       The name refers to the saying, "If it looks like a duck, swims like a duck, and quacks
       like a duck, then it probably is a duck". Duck typing can be a more flexible way of
       testing objects than relying on "isa", as it allows people to easily substitute mock
       objects.

       This package inherits from Type::Tiny; see that for most documentation.  Major differences
       are listed below:

   Attributes
       "methods"
           An arrayref of method names.

       "constraint"
           Unlike Type::Tiny, you cannot pass a constraint coderef to the constructor.  Instead
           rely on the default.

       "inlined"
           Unlike Type::Tiny, you cannot pass an inlining coderef to the constructor.  Instead
           rely on the default.

       "parent"
           Parent is always Types::Standard::Object, and cannot be passed to the constructor.

   Methods
       "stringifies_to($constraint)"
           See Type::Tiny::ConstrainedObject.

       "numifies_to($constraint)"
           See Type::Tiny::ConstrainedObject.

       "with_attribute_values($attr1 => $constraint1, ...)"
           See Type::Tiny::ConstrainedObject.

   Exports
       Type::Tiny::Duck can be used as an exporter.

         use Type::Tiny::Duck HttpClient => [ 'get', 'post' ];

       This will export the following functions into your namespace:

       "HttpClient"
       "is_HttpClient( $value )"
       "assert_HttpClient( $value )"
       "to_HttpClient( $value )"

       Multiple types can be exported at once:

         use Type::Tiny::Duck (
           HttpClient   => [ 'get', 'post' ],
           FtpClient    => [ 'upload', 'download' ],
         );

BUGS

       Please report any bugs to <https://github.com/tobyink/p5-type-tiny/issues>.

SEE ALSO

       Type::Tiny::Manual.

       Type::Tiny.

       Moose::Meta::TypeConstraint::DuckType.

AUTHOR

       Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

       This software is copyright (c) 2013-2014, 2017-2023 by Toby Inkster.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

       THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
       WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
       PURPOSE.