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.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
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.\" ========================================================================
.\"
.IX Title "Type::Tiny::Duck 3pm"
.TH Type::Tiny::Duck 3pm "2023-07-21" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Type::Tiny::Duck \- type constraints based on the "can" method
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
Using via Types::Standard:
.PP
.Vb 3
\&  package Logger {
\&    use Moo;
\&    use Types::Standard qw( HasMethods Bool );
\&    
\&    has debugging => ( is => \*(Aqrw\*(Aq, isa => Bool, default => 0 );
\&    has output    => ( is => \*(Aqro\*(Aq, isa => HasMethods[ \*(Aqprint\*(Aq ] );
\&    
\&    sub warn {
\&      my ( $self, $message ) = @_;
\&      $self\->output\->print( "[WARNING] $message\en" );
\&    }
\&    
\&    sub debug {
\&      my ( $self, $message ) = @_;
\&      $self\->output\->print( "[DEBUG] $message\en" ) if $self\->debugging;
\&    }
\&  }
.Ve
.PP
Using Type::Tiny::Duck's export feature:
.PP
.Vb 4
\&  package Logger {
\&    use Moo;
\&    use Types::Standard qw( Bool );
\&    use Type::Tiny::Duck Printable => [ \*(Aqprint\*(Aq ];
\&    
\&    has debugging => ( is => \*(Aqrw\*(Aq, isa => Bool, default => 0 );
\&    has output    => ( is => \*(Aqro\*(Aq, isa => Printable );
\&    
\&    sub warn {
\&      my ( $self, $message ) = @_;
\&      $self\->output\->print( "[WARNING] $message\en" );
\&    }
\&    
\&    sub debug {
\&      my ( $self, $message ) = @_;
\&      $self\->output\->print( "[DEBUG] $message\en" ) if $self\->debugging;
\&    }
\&  }
.Ve
.PP
Using Type::Tiny::Duck's object-oriented interface:
.PP
.Vb 4
\&  package Logger {
\&    use Moo;
\&    use Types::Standard qw( Bool );
\&    use Type::Tiny::Duck;
\&    
\&    my $Printable = Type::Type::Duck\->new(
\&      name    => \*(AqPrintable\*(Aq,
\&      methods => [ \*(Aqprint\*(Aq ],
\&    );
\&    
\&    has debugging => ( is => \*(Aqrw\*(Aq, isa => Bool, default => 0 );
\&    has output    => ( is => \*(Aqro\*(Aq, isa => $Printable );
\&    
\&    sub warn {
\&      my ( $self, $message ) = @_;
\&      $self\->output\->print( "[WARNING] $message\en" );
\&    }
\&    
\&    sub debug {
\&      my ( $self, $message ) = @_;
\&      $self\->output\->print( "[DEBUG] $message\en" ) if $self\->debugging;
\&    }
\&  }
.Ve
.SH "STATUS"
.IX Header "STATUS"
This module is covered by the
Type-Tiny stability policy.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Type constraints of the general form \f(CW\*(C`{ $_\->can("method") }\*(C'\fR.
.PP
The name refers to the saying, \*(L"If it looks like a duck, swims like a duck,
and quacks like a duck, then it probably is a duck\*(R". Duck typing can be
a more flexible way of testing objects than relying on \f(CW\*(C`isa\*(C'\fR, as it allows
people to easily substitute mock objects.
.PP
This package inherits from Type::Tiny; see that for most documentation.
Major differences are listed below:
.SS "Attributes"
.IX Subsection "Attributes"
.ie n .IP """methods""" 4
.el .IP "\f(CWmethods\fR" 4
.IX Item "methods"
An arrayref of method names.
.ie n .IP """constraint""" 4
.el .IP "\f(CWconstraint\fR" 4
.IX Item "constraint"
Unlike Type::Tiny, you \fIcannot\fR pass a constraint coderef to the constructor.
Instead rely on the default.
.ie n .IP """inlined""" 4
.el .IP "\f(CWinlined\fR" 4
.IX Item "inlined"
Unlike Type::Tiny, you \fIcannot\fR pass an inlining coderef to the constructor.
Instead rely on the default.
.ie n .IP """parent""" 4
.el .IP "\f(CWparent\fR" 4
.IX Item "parent"
Parent is always \fBTypes::Standard::Object\fR, and cannot be passed to the
constructor.
.SS "Methods"
.IX Subsection "Methods"
.ie n .IP """stringifies_to($constraint)""" 4
.el .IP "\f(CWstringifies_to($constraint)\fR" 4
.IX Item "stringifies_to($constraint)"
See Type::Tiny::ConstrainedObject.
.ie n .IP """numifies_to($constraint)""" 4
.el .IP "\f(CWnumifies_to($constraint)\fR" 4
.IX Item "numifies_to($constraint)"
See Type::Tiny::ConstrainedObject.
.ie n .IP """with_attribute_values($attr1 => $constraint1, ...)""" 4
.el .IP "\f(CWwith_attribute_values($attr1 => $constraint1, ...)\fR" 4
.IX Item "with_attribute_values($attr1 => $constraint1, ...)"
See Type::Tiny::ConstrainedObject.
.SS "Exports"
.IX Subsection "Exports"
Type::Tiny::Duck can be used as an exporter.
.PP
.Vb 1
\&  use Type::Tiny::Duck HttpClient => [ \*(Aqget\*(Aq, \*(Aqpost\*(Aq ];
.Ve
.PP
This will export the following functions into your namespace:
.ie n .IP """HttpClient""" 4
.el .IP "\f(CWHttpClient\fR" 4
.IX Item "HttpClient"
.PD 0
.ie n .IP """is_HttpClient( $value )""" 4
.el .IP "\f(CWis_HttpClient( $value )\fR" 4
.IX Item "is_HttpClient( $value )"
.ie n .IP """assert_HttpClient( $value )""" 4
.el .IP "\f(CWassert_HttpClient( $value )\fR" 4
.IX Item "assert_HttpClient( $value )"
.ie n .IP """to_HttpClient( $value )""" 4
.el .IP "\f(CWto_HttpClient( $value )\fR" 4
.IX Item "to_HttpClient( $value )"
.PD
.PP
Multiple types can be exported at once:
.PP
.Vb 4
\&  use Type::Tiny::Duck (
\&    HttpClient   => [ \*(Aqget\*(Aq, \*(Aqpost\*(Aq ],
\&    FtpClient    => [ \*(Aqupload\*(Aq, \*(Aqdownload\*(Aq ],
\&  );
.Ve
.SH "BUGS"
.IX Header "BUGS"
Please report any bugs to
<https://github.com/tobyink/p5\-type\-tiny/issues>.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Type::Tiny::Manual.
.PP
Type::Tiny.
.PP
Moose::Meta::TypeConstraint::DuckType.
.SH "AUTHOR"
.IX Header "AUTHOR"
Toby Inkster <tobyink@cpan.org>.
.SH "COPYRIGHT AND LICENCE"
.IX Header "COPYRIGHT AND LICENCE"
This software is copyright (c) 2013\-2014, 2017\-2023 by Toby Inkster.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
.SH "DISCLAIMER OF WARRANTIES"
.IX Header "DISCLAIMER OF WARRANTIES"
\&\s-1THIS PACKAGE IS PROVIDED \*(L"AS IS\*(R" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.\s0