# PODNAME: Moose::Cookbook::Snack::Types
# ABSTRACT: Snippets of code for using Types and Type Constraints



=encoding UTF-8

=head1 NAME

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

=head1 VERSION

version 2.2011


  package Point;
  use Moose;

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

  package main;
  use Try::Tiny;

  my $point = try {
      Point->new( x => 'fifty', y => 'forty' );
  catch {
      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";


This is the Point example from
L<Moose::Cookbook::Basics::Point_AttributesAndSubclassing> with type checking

If we try to assign a string value to an attribute that is an C<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 L<Try::Tiny> to catch this error message.

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

=head1 SEE ALSO

=over 4

=item L<Moose::Cookbook::Basics::Point_AttributesAndSubclassing>

=item L<Moose::Util::TypeConstraints>

=item L<Moose::Meta::Attribute>


=head1 AUTHORS

=over 4

=item *

Stevan Little <stevan.little@iinteractive.com>

=item *

Dave Rolsky <autarch@urth.org>

=item *

Jesse Luehrs <doy@tozt.net>

=item *

Shawn M Moore <code@sartak.org>

=item *

יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>

=item *

Karen Etheridge <ether@cpan.org>

=item *

Florian Ragwitz <rafl@debian.org>

=item *

Hans Dieter Pearcey <hdp@weftsoar.net>

=item *

Chris Prather <chris@prather.org>

=item *

Matt S Trout <mst@shadowcat.co.uk>



This software is copyright (c) 2006 by Infinity Interactive, Inc.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.