| Moose::Cookbook::Snack::Types - Snippets of code for using Types and Type Constraints |
Moose::Cookbook::Snack::Types - Snippets of code for using Types and Type Constraints
package Point;
use Moose;
has 'x' => (isa => 'Int', is => 'ro' );
has 'y' => (isa => 'Int', is => 'rw' );
package main;
my $point = eval {
Point->new(x => 'fifty', y => 'fourty');
};
if($@) {
print "Oops: $@";
}
my $point;
my $xval = 'fourty-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 (the Moose::Cookbook::Recipe1 manpage) with added type checking.
If we try to assign a string value to an attribute that is defined as being of type Int, Moose will die with an explicit error message saying which attribute failed which type constaint with which value. The eval example catches this message and displays it.
The second example fetches the type constraint instance and asks it to check the value we are about to set, before we try and set it.
Jess Robinson <cpan@desert-island.me.uk>
Copyright 2006-2008 by Infinity Interactive, Inc.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
| Moose::Cookbook::Snack::Types - Snippets of code for using Types and Type Constraints |