Module::Pluggable - automatically give your module the ability to have plugins
Simple use Module::Pluggable -
package MyClass;
use Module::Pluggable;
and then later ...
use MyClass;
my $mc = MyClass->new();
# returns the names of all plugins installed under MyClass::Plugin::*
my @plugins = $mc->plugins();
Why would you want to do this? Say you have something that wants to pass an object to a number of different plugins in turn. For example you may want to extract meta-data from every email you get sent and do something with it. Plugins make sense here because then you can keep adding new meta data parsers and all the logic and docs for each one will be self contained and new handlers are easy to add without changing the core code. For that, you might do something like ...
package Email::Examiner;
use strict;
use Email::Simple;
use Module::Pluggable require => 1;
sub handle_email {
my $self = shift;
my $email = shift;
foreach my $plugin ($self->plugins) {
$plugin->examine($email);
}
return 1;
}
.. and all the plugins will get a chance in turn to look at it.
This can be trivally extended so that plugins could save the email
somewhere and then no other plugin should try and do that.
Simply have it so that the examine method returns 1 if
it has saved the email somewhere. You might also wnat to be paranoid
and check to see if the plugin has an examine method.
foreach my $plugin ($self->plugins) {
next unless $plugin->can('examine');
last if $plugin->examine($email);
}
And so on. The sky's the limit.
Provides a simple but, hopefully, extensible way of having 'plugins' for your module. Obviously this isn't going to be the be all and end all of solutions but it works for me.
Essentially all it does is export a method into your namespace that looks through a search path for .pm files and turn those into class names.
Optionally it instantiates those classes for you.
Alternatively, if you don't want to use 'plugins' as the method ...
package MyClass;
use Module::Pluggable sub_name => 'foo';
and then later ...
my @plugins = $mc->foo();
Or if you want to look in another namespace
package MyClass;
use Module::Pluggable search_path => ['Acme::MyClass::Plugin', 'MyClass::Extend'];
or directory
use Module::Pluggable search_dirs => ['mylibs/Foo'];
Or if you want to instantiate each plugin rather than just return the name
package MyClass;
use Module::Pluggable instantiate => 'new';
and then
# whatever is passed to 'plugins' will be passed
# to 'new' for each plugin
my @plugins = $mc->plugins(@options);
alternatively you can just require the module without instantiating it
package MyClass;
use Module::Pluggable require => 1;
since requiring automatically searches inner packages, which may not be desirable, you can turn this off
package MyClass;
use Module::Pluggable require => 1, inner => 0;
You can limit the plugins loaded using the except option, either as a string, array ref or regex
package MyClass;
use Module::Pluggable except => 'MyClass::Plugin::Foo';
or
package MyClass;
use Module::Pluggable except => ['MyClass::Plugin::Foo', 'MyClass::Plugin::Bar'];
or
package MyClass;
use Module::Pluggable except => qr/^MyClass::Plugin::(Foo|Bar)$/;
and similarly for only which will only load plugins which match.
Remember you can use the module more than once
package MyClass;
use Module::Pluggable search_path => 'MyClass::Filters' sub_name => 'filters';
use Module::Pluggable search_path => 'MyClass::Plugins' sub_name => 'plugins';
and then later ...
my @filters = $self->filters;
my @plugins = $self->plugins;
If you have, for example, a file lib/Something/Plugin/Foo.pm that
contains package definitions for both Something::Plugin::Foo and
Something::Plugin::Bar then as long as you either have either
the require or instantiate option set then we'll also find
Something::Plugin::Bar. Nifty!
You can pass a hash of options when importing this module.
The options can be ...
The name of the subroutine to create in your namespace.
By default this is 'plugins'
An array ref of namespaces to look in.
An array ref of directorys to look in before @INC.
Call this method on the class. In general this will probably be 'new' but it can be whatever you want. Whatever arguments are passed to 'plugins' will be passed to the method.
The default is 'undef' i.e just return the class name.
Just require the class, don't instantiate (overrides 'instantiate');
If set to 0 will not search inner packages.
If set to 1 will override require.
Takes a string, array ref or regex describing the names of the only plugins to return. Whilst this may seem perverse ... well, it is. But it also makes sense. Trust me.
Similar to only it takes a description of plugins to exclude
from returning. This is slightly less perverse.
This is for use by extension modules which build on Module::Pluggable:
passing a package option allows you to place the plugin method in a
different package other than your own.
By default Module::Pluggable only looks for .pm files.
By supplying a new file_regex then you can change this behaviour e.g
file_regex => qr/\.plugin$/
By default Module::Pluggable ignores files that look like they were
left behind by editors. Currently this means files ending in ~ (~),
the extensions .swp or .swo, or files beginning with .#.
Setting include_editor_junk changes Module::Pluggable so it does
not ignore any files it finds.
The method search_path is exported into you namespace as well.
You can call that at any time to change or replace the
search_path.
$self->search_path( add => "New::Path" ); # add
$self->search_path( new => "New::Path" ); # replace
This does everything I need and I can't really think of any other features I want to add. Famous last words of course
Recently tried fixed to find inner packages and to make it 'just work' with PAR but there are still some issues.
However suggestions (and patches) are welcome.
Simon Wistow <simon@thegestalt.org>
Copyright, 2006 Simon Wistow
Distributed under the same terms as Perl itself.
None known.
File::Spec, File::Find, File::Basename, Class::Factory::Util, Module::Pluggable::Ordered