Type-Tiny — Type::Tiny::Duck

Synopsis

  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' ],
  );