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.\" ========================================================================
.\"
.IX Title "Moose::Cookbook::Snack::Types 3pm"
.TH Moose::Cookbook::Snack::Types 3pm "2012-06-28" "perl v5.14.2" "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"
Moose::Cookbook::Snack::Types \- Snippets of code for using Types and Type Constraints
.SH "VERSION"
.IX Header "VERSION"
version 2.0603
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&  package Point;
\&  use Moose;
\&
\&  has \*(Aqx\*(Aq => ( isa => \*(AqInt\*(Aq, is => \*(Aqro\*(Aq );
\&  has \*(Aqy\*(Aq => ( isa => \*(AqInt\*(Aq, is => \*(Aqrw\*(Aq );
\&
\&  package main;
\&  use Try::Tiny;
\&
\&  my $point = try {
\&      Point\->new( x => \*(Aqfifty\*(Aq, y => \*(Aqforty\*(Aq );
\&  }
\&  catch {
\&      print "Oops: $_";
\&  };
\&
\&  my $point;
\&  my $xval             = \*(Aqforty\-two\*(Aq;
\&  my $xattribute       = Point\->meta\->find_attribute_by_name(\*(Aqx\*(Aq);
\&  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 . "\en";
\&  }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is the Point example from
Moose::Cookbook::Basics::Point_AttributesAndSubclassing with type checking
added.
.PP
If we try to assign a string value to an attribute that is an \f(CW\*(C`Int\*(C'\fR,
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.
.PP
We use Try::Tiny to catch this error message.
.PP
Later, we get the Moose::Meta::TypeConstraint object from a
Moose::Meta::Attribute and use the Moose::Meta::TypeConstraint
to check a value directly.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP "Moose::Cookbook::Basics::Point_AttributesAndSubclassing" 4
.IX Item "Moose::Cookbook::Basics::Point_AttributesAndSubclassing"
.PD 0
.IP "Moose::Utils::TypeConstraints" 4
.IX Item "Moose::Utils::TypeConstraints"
.IP "Moose::Meta::Attribute" 4
.IX Item "Moose::Meta::Attribute"
.PD
.SH "AUTHOR"
.IX Header "AUTHOR"
Moose is maintained by the Moose Cabal, along with the help of many contributors. See \*(L"\s-1CABAL\s0\*(R" in Moose and \*(L"\s-1CONTRIBUTORS\s0\*(R" in Moose for details.
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2012 by Infinity Interactive, Inc..
.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.