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Stevan Little
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NAME

Moose::Cookbook::Snack::Types - Snippets of code for using Types and Type Constraints

SYNOPSIS

  package Point;
  use Moose;

  has 'x' => ( isa => 'Int', is => 'ro' );
  has 'y' => ( isa => 'Int', is => 'rw' );

  package main;

  my $point = eval { Point->new( x => 'fifty', y => 'forty' ); };

  if ($@) {
      print "Oops: $@";
  }

  my $point;
  my $xval             = 'forty-two';
  my $xattribute       = Point->meta->find_attribute_by_name('x');
  my $xtype_constraint = $xattribute->type_constraint;

  if ( $xtype_constraint->check($xval) ) {
      $point = Point->new( x => $xval, y => 0 );
  }
  else {
      print "Value: $xval is not an " . $xtype_constraint->name . "\n";
  }

DESCRIPTION

This is the Point example from Moose::Cookbook::Basics::Recipe1 with type checking added.

If we try to assign a string value to an attribute that is an Int, Moose will die with an explicit error message. The error will include the attribute name, as well as the type constraint name and the value which failed the constraint check.

We use eval to catch this error message in $@.

Later, we get the Moose::Meta::TypeConstraint object from a Moose::Meta::Attribute and use the Moose::Meta::TypeConstraint to check a value directly.

SEE ALSO

Moose::Cookbook::Basics::Recipe1
Moose::Utils::TypeConstraints
Moose::Meta::Attribute

AUTHOR

Jess Robinson <cpan@desert-island.me.uk>

COPYRIGHT AND LICENSE

Copyright 2006-2010 by Infinity Interactive, Inc.

http://www.iinteractive.com

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