perldoc > Type::Tiny::Duck(3pm)

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 AT 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.