Module::Pluggable(3) User Contributed Perl Documentation Module::Pluggable(3)
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();
EEXXAAMMPPLLEE
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 handleemail {
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.
AADDVVAANNCCEEDD UUSSAAGGEE
Alternatively, if you don't want to use 'plugins' as the method ...
package MyClass;
use Module::Pluggable subname => 'foo';
and then later ...
my @plugins = $mc->foo();
Or if you want to look in another namespace
package MyClass;
use Module::Pluggable searchpath => ['Acme::MyClass::Plugin', 'MyClass::Extend'];
or directory
use Module::Pluggable searchdirs => ['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 searchpath => 'MyClass::Filters' subname => 'filters';
use Module::Pluggable searchpath => 'MyClass::Plugins' subname => 'plugins';
and then later ...
my @filters = $self->filters;
my @plugins = $self->plugins;
IINNNNEERR PPAACCKKAAGGEESS
If you have, for example, a file lliibb//SSoommeetthhiinngg//PPlluuggiinn//FFoooo..ppmm that
contains package definitions for both "Something::Plugin::Foo" and
"Something::Plugin::Bar" then as long as you either have either the
rreeqquuiirree or iinnssttaannttiiaattee option set then we'll also find
"Something::Plugin::Bar". Nifty!
OOPPTTIIOONNSS
You can pass a hash of options when importing this module.
The options can be ...
ssuubbnnaammee
The name of the subroutine to create in your namespace.
By default this is 'plugins'
sseeaarrcchhppaatthh
An array ref of namespaces to look in.
sseeaarrcchhddiirrss
An array ref of directorys to look in before @INC.
iinnssttaannttiiaattee
Call this method on the class. In general this will probably be 'new'
but it can be whatever you want. Whatever arguments are passed to
'plugins' will be passed to the method.
The default is 'undef' i.e just return the class name.
rreeqquuiirree
Just require the class, don't instantiate (overrides 'instantiate');
iinnnneerr
If set to 0 will nnoott search inner packages. If set to 1 will override
"require".
oonnllyy
Takes a string, array ref or regex describing the names of the only
plugins to return. Whilst this may seem perverse ... well, it is. But
it also makes sense. Trust me.
eexxcceepptt
Similar to "only" it takes a description of plugins to exclude from
returning. This is slightly less perverse.
ppaacckkaaggee
This is for use by extension modules which build on
"Module::Pluggable": passing a "package" option allows you to place the
plugin method in a different package other than your own.
ffiilleerreeggeexx
By default "Module::Pluggable" only looks for .pm files.
By supplying a new "fileregex" then you can change this behaviour e.g
fileregex => qr/\.plugin$/
MMEETTHHOODDss
sseeaarrcchhppaatthh
The method "searchpath" is exported into you namespace as well. You
can call that at any time to change or replace the searchpath.
$self->searchpath( add => "New::Path" ); # add
$self->searchpath( new => "New::Path" ); # replace
FFUUTTUURREE PPLLAANNSS
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
CCOOPPYYIINNGG
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 v5.8.8 2007-01-29 Module::Pluggable(3)