NAME¶
Moose::Cookbook::Extending::Debugging_BaseClassRole - Providing a role for the
base object class
VERSION¶
version 2.1213
SYNOPSIS¶
package MooseX::Debugging;
use Moose::Exporter;
Moose::Exporter->setup_import_methods(
base_class_roles => ['MooseX::Debugging::Role::Object'],
);
package MooseX::Debugging::Role::Object;
use Moose::Role;
sub BUILD {}
after BUILD => sub {
my $self = shift;
warn "Made a new " . ( ref $self ) . " object\n";
};
DESCRIPTION¶
In this example, we provide a role for the base object class that adds some
simple debugging output. Every time an object is created, it spits out a
warning saying what type of object it was.
Obviously, a real debugging role would do something more interesting, but this
recipe is all about how we apply that role.
In this case, with the combination of Moose::Exporter and Moose::Util::MetaRole,
we ensure that when a module does "use MooseX::Debugging", it
automatically gets the debugging role applied to its base object class.
There are a few pieces of code worth looking at more closely.
Moose::Exporter->setup_import_methods(
base_class_roles => ['MooseX::Debugging::Role::Object'],
);
This creates an "import" method in the "MooseX::Debugging"
package. Since we are not actually exporting anything, we do not pass
"setup_import_methods" any parameters related to exports, but we
need to have an "import" method to ensure that our
"init_meta" method is called. The "init_meta" is created
by "setup_import_methods" for us, since we passed the
"base_class_roles" parameter. The generated "init_meta"
will in turn call Moose::Util::MetaRole::apply_base_class_roles.
sub BUILD {}
after BUILD => sub {
...
};
Due to the way role composition currently works, if the class that a role is
composed into contains a "BUILD" method, then that will override the
"BUILD" method in any roles it composes, which is typically not what
you want. Using a method modifier on "BUILD" avoids this issue,
since method modifiers compose together rather than being overridden. Method
modifiers require that a method exists in order to wrap, however, so we also
provide a stub method to wrap if no "BUILD" method exists in the
class.
AUTHORS¶
- •
- Stevan Little <stevan.little@iinteractive.com>
- •
- Dave Rolsky <autarch@urth.org>
- •
- Jesse Luehrs <doy@tozt.net>
- •
- Shawn M Moore <code@sartak.org>
- •
- XXXX XXX'XX (Yuval Kogman) <nothingmuch@woobling.org>
- •
- Karen Etheridge <ether@cpan.org>
- •
- Florian Ragwitz <rafl@debian.org>
- •
- Hans Dieter Pearcey <hdp@weftsoar.net>
- •
- Chris Prather <chris@prather.org>
- •
- Matt S Trout <mst@shadowcat.co.uk>
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.