Moose::Cookbook::Basics::Immutable3pm

Usage

  package Point;
  use Moose;
  has 'x' => ( isa => 'Int', is => 'ro' );
  has 'y' => ( isa => 'Int', is => 'rw' );
  __PACKAGE__->meta->make_immutable;

Version

version 2.4001

Overview

The Moose metaclass API provides a make_immutable() method. Calling this method does two things to your class. First, it makes it faster. In particular, object construction and destruction are effectively "inlined" in your class, and no longer invoke the meta API.

Second, you can no longer make changes via the metaclass API, such as adding attributes. In practice, this won't be a problem, as you rarely need to do this after first loading the class.

Conclusion

We strongly recommend you make your classes immutable. It makes your code much faster, with a small compile-time cost. This will be especially noticeable when creating many objects.

Copyright and license

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.