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Module::Pluggable(3pm) Perl Programmers Reference Guide Module::Pluggable(3pm)

NAME
       Module::Pluggable - automatically give your module the ability to have
       plugins

SYNOPSIS
       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();

EXAMPLE
       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.

DESCRIPTION
       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.

ADVANCED USAGE
       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;

INNER PACKAGES
       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!

OPTIONS
       You can pass a hash of options when importing this module.

       The options can be ...

   sub_name
       The name of the subroutine to create in your namespace.

       By default this is 'plugins'

   search_path
       An array ref of namespaces to look in.

   search_dirs
       An array ref of directorys to look in before @INC.

   instantiate
       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.

   require
       Just require the class, don't instantiate (overrides 'instantiate');

   inner
       If set to 0 will not search inner packages.  If set to 1 will override
       "require".

   only
       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.

   except
       Similar to "only" it takes a description of plugins to exclude from
       returning. This is slightly less perverse.

   package
       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.

   file_regex
       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$/

   include_editor_junk
       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.

METHODs
   search_path
       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

FUTURE PLANS
       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.

AUTHOR
       Simon Wistow <simon@thegestalt.org>

COPYING
       Copyright, 2006 Simon Wistow

       Distributed under the same terms as Perl itself.

BUGS
       None known.

SEE ALSO
       File::Spec, File::Find, File::Basename, Class::Factory::Util,
       Module::Pluggable::Ordered

perl v5.16.3			  2013-03-04		Module::Pluggable(3pm)
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