Module::Pluggable(3pm)

1Module::Pluggable(3)  User Contributed Perl Documentation Module::Pluggable(3)
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NAME

6       Module::Pluggable - automatically give your module the ability to have
7       plugins
8

SYNOPSIS

10       Simple use Module::Pluggable -
11
12           package MyClass;
13           use Module::Pluggable;
14
15       and then later ...
16
17           use MyClass;
18           my $mc = MyClass->new();
19           # returns the names of all plugins installed under MyClass::Plugin::*
20           my @plugins = $mc->plugins();
21

EXAMPLE

23       Why would you want to do this? Say you have something that wants to
24       pass an object to a number of different plugins in turn. For example
25       you may want to extract meta-data from every email you get sent and do
26       something with it. Plugins make sense here because then you can keep
27       adding new meta data parsers and all the logic and docs for each one
28       will be self contained and new handlers are easy to add without chang‐
29       ing the core code. For that, you might do something like ...
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31           package Email::Examiner;
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33           use strict;
34           use Email::Simple;
35           use Module::Pluggable require => 1;
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37           sub handle_email {
38               my $self  = shift;
39               my $email = shift;
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41               foreach my $plugin ($self->plugins) {
42                   $plugin->examine($email);
43               }
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45               return 1;
46           }
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48       .. and all the plugins will get a chance in turn to look at it.
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50       This can be trivally extended so that plugins could save the email
51       somewhere and then no other plugin should try and do that.  Simply have
52       it so that the "examine" method returns 1 if it has saved the email
53       somewhere. You might also wnat to be paranoid and check to see if the
54       plugin has an "examine" method.
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56               foreach my $plugin ($self->plugins) {
57                   next unless $plugin->can('examine');
58                   last if     $plugin->examine($email);
59               }
60
61       And so on. The sky's the limit.
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DESCRIPTION

64       Provides a simple but, hopefully, extensible way of having 'plugins'
65       for your module. Obviously this isn't going to be the be all and end
66       all of solutions but it works for me.
67
68       Essentially all it does is export a method into your namespace that
69       looks through a search path for .pm files and turn those into class
70       names.
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72       Optionally it instantiates those classes for you.
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ADVANCED USAGE

75       Alternatively, if you don't want to use 'plugins' as the method ...
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77           package MyClass;
78           use Module::Pluggable sub_name => 'foo';
79
80       and then later ...
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82           my @plugins = $mc->foo();
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84       Or if you want to look in another namespace
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86           package MyClass;
87           use Module::Pluggable search_path => ['Acme::MyClass::Plugin', 'MyClass::Extend'];
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89       or directory
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91           use Module::Pluggable search_dirs => ['mylibs/Foo'];
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93       Or if you want to instantiate each plugin rather than just return the
94       name
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96           package MyClass;
97           use Module::Pluggable instantiate => 'new';
98
99       and then
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101           # whatever is passed to 'plugins' will be passed
102           # to 'new' for each plugin
103           my @plugins = $mc->plugins(@options);
104
105       alternatively you can just require the module without instantiating it
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107           package MyClass;
108           use Module::Pluggable require => 1;
109
110       since requiring automatically searches inner packages, which may not be
111       desirable, you can turn this off
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113           package MyClass;
114           use Module::Pluggable require => 1, inner => 0;
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116       You can limit the plugins loaded using the except option, either as a
117       string, array ref or regex
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119           package MyClass;
120           use Module::Pluggable except => 'MyClass::Plugin::Foo';
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122       or
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124           package MyClass;
125           use Module::Pluggable except => ['MyClass::Plugin::Foo', 'MyClass::Plugin::Bar'];
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127       or
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129           package MyClass;
130           use Module::Pluggable except => qr/^MyClass::Plugin::(Foo⎪Bar)$/;
131
132       and similarly for only which will only load plugins which match.
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134       Remember you can use the module more than once
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136           package MyClass;
137           use Module::Pluggable search_path => 'MyClass::Filters' sub_name => 'filters';
138           use Module::Pluggable search_path => 'MyClass::Plugins' sub_name => 'plugins';
139
140       and then later ...
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142           my @filters = $self->filters;
143           my @plugins = $self->plugins;
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INNER PACKAGES

146       If you have, for example, a file lib/Something/Plugin/Foo.pm that con‐
147       tains package definitions for both "Something::Plugin::Foo" and "Some‐
148       thing::Plugin::Bar" then as long as you either have either the require
149       or instantiate option set then we'll also find "Something::Plug‐
150       in::Bar". Nifty!
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OPTIONS

153       You can pass a hash of options when importing this module.
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155       The options can be ...
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157       sub_name
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159       The name of the subroutine to create in your namespace.
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161       By default this is 'plugins'
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163       search_path
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165       An array ref of namespaces to look in.
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167       search_dirs
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169       An array ref of directorys to look in before @INC.
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171       instantiate
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173       Call this method on the class. In general this will probably be 'new'
174       but it can be whatever you want. Whatever arguments are passed to
175       'plugins' will be passed to the method.
176
177       The default is 'undef' i.e just return the class name.
178
179       require
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181       Just require the class, don't instantiate (overrides 'instantiate');
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183       inner
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185       If set to 0 will not search inner packages.  If set to 1 will override
186       "require".
187
188       only
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190       Takes a string, array ref or regex describing the names of the only
191       plugins to return. Whilst this may seem perverse ... well, it is. But
192       it also makes sense. Trust me.
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194       except
195
196       Similar to "only" it takes a description of plugins to exclude from
197       returning. This is slightly less perverse.
198
199       package
200
201       This is for use by extension modules which build on "Module::Plug‐
202       gable": passing a "package" option allows you to place the plugin
203       method in a different package other than your own.
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205       file_regex
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207       By default "Module::Pluggable" only looks for .pm files.
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209       By supplying a new "file_regex" then you can change this behaviour e.g
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211           file_regex => qr/\.plugin$/
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METHODs

214       search_path
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216       The method "search_path" is exported into you namespace as well.  You
217       can call that at any time to change or replace the search_path.
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219           $self->search_path( add => "New::Path" ); # add
220           $self->search_path( new => "New::Path" ); # replace
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FUTURE PLANS

223       This does everything I need and I can't really think of any other fea‐
224       tures I want to add. Famous last words of course
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226       Recently tried fixed to find inner packages and to make it 'just work'
227       with PAR but there are still some issues.
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229       However suggestions (and patches) are welcome.
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AUTHOR

232       Simon Wistow <simon@thegestalt.org>
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COPYING

235       Copyright, 2006 Simon Wistow
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237       Distributed under the same terms as Perl itself.
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BUGS

240       None known.
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