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

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 the Moose::Cookbook::Basics::Recipe1 manpage 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 the Moose::Meta::TypeConstraint manpage object from a the Moose::Meta::Attribute manpage and use the the Moose::Meta::TypeConstraint manpage to check a value directly.

AUTHOR

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

COPYRIGHT AND LICENSE

http://www.iinteractive.com