#NAME

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

#VERSION

version 2.2207

#SYNOPSIS

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";
}

#DESCRIPTION

This is the Point example from Moose::Cookbook::Basics::Point_AttributesAndSubclassing 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 Try::Tiny to catch this error message.

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::Point_AttributesAndSubclassing
#Moose::Util::TypeConstraints
#Moose::Meta::Attribute

#AUTHORS

Stevan Little <stevan@cpan.org>
Dave Rolsky <autarch@urth.org>
Jesse Luehrs <doy@cpan.org>
Shawn M Moore <sartak@cpan.org>
יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
Karen Etheridge <ether@cpan.org>
Florian Ragwitz <rafl@debian.org>
Hans Dieter Pearcey <hdp@cpan.org>
Chris Prather <chris@prather.org>
Matt S Trout <mstrout@cpan.org>

#COPYRIGHT AND LICENSE

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