Type::Tiny::Duck - type constraints based on the "can" method
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; } }
This module is covered by the Type-Tiny stability policy.
Type constraints of the general form { $_->can("method") }.
{ $_->can("method") }
The name refers to the saying, "If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck". Duck typing can be a more flexible way of testing objects than relying on isa, as it allows people to easily substitute mock objects.
isa
This package inherits from Type::Tiny; see that for most documentation. Major differences are listed below:
methods
An arrayref of method names.
constraint
Unlike Type::Tiny, you cannot pass a constraint coderef to the constructor. Instead rely on the default.
inlined
Unlike Type::Tiny, you cannot pass an inlining coderef to the constructor. Instead rely on the default.
parent
Parent is always Types::Standard::Object, and cannot be passed to the constructor.
stringifies_to($constraint)
See Type::Tiny::ConstrainedObject.
numifies_to($constraint)
with_attribute_values($attr1 => $constraint1, ...)
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' ], );
Please report any bugs to https://github.com/tobyink/p5-type-tiny/issues.
Type::Tiny::Manual.
Type::Tiny.
Moose::Meta::TypeConstraint::DuckType.
Toby Inkster <tobyink@cpan.org>.
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.
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.
To install Type::Tiny, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Type::Tiny
CPAN shell
perl -MCPAN -e shell install Type::Tiny
For more information on module installation, please visit the detailed CPAN module installation guide.