Module::Pluggable(3pm)

1Module::Pluggable(3pm) Perl Programmers Reference Guide Module::Pluggable(3pm)
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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
29       changing 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               }
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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 = $mc->plugins(@options);
104
105       alternatively you can just require the module without instantiating it
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107           package MyClass;
108           use Module::Pluggable require => 1;
109
110       since requiring automatically searches inner packages, which may not be
111       desirable, you can turn this off
112
113           package MyClass;
114           use Module::Pluggable require => 1, inner => 0;
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116       You can limit the plugins loaded using the except option, either as a
117       string, array ref or regex
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119           package MyClass;
120           use Module::Pluggable except => 'MyClass::Plugin::Foo';
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122       or
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124           package MyClass;
125           use Module::Pluggable except => ['MyClass::Plugin::Foo', 'MyClass::Plugin::Bar'];
126
127       or
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129           package MyClass;
130           use Module::Pluggable except => qr/^MyClass::Plugin::(Foo|Bar)$/;
131
132       and similarly for only which will only load plugins which match.
133
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
147       contains package definitions for both "Something::Plugin::Foo" and
148       "Something::Plugin::Bar" then as long as you either have either the
149       require or instantiate option set then we'll also find
150       "Something::Plugin::Bar". Nifty!
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OPTIONS

153       You can pass a hash of options when importing this module.
154
155       The options can be ...
156
157   sub_name
158       The name of the subroutine to create in your namespace.
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160       By default this is 'plugins'
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162   search_path
163       An array ref of namespaces to look in.
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165   search_dirs
166       An array ref of directorys to look in before @INC.
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168   instantiate
169       Call this method on the class. In general this will probably be 'new'
170       but it can be whatever you want. Whatever arguments are passed to
171       'plugins' will be passed to the method.
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173       The default is 'undef' i.e just return the class name.
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175   require
176       Just require the class, don't instantiate (overrides 'instantiate');
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178   inner
179       If set to 0 will not search inner packages.  If set to 1 will override
180       "require".
181
182   only
183       Takes a string, array ref or regex describing the names of the only
184       plugins to return. Whilst this may seem perverse ... well, it is. But
185       it also makes sense. Trust me.
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187   except
188       Similar to "only" it takes a description of plugins to exclude from
189       returning. This is slightly less perverse.
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191   package
192       This is for use by extension modules which build on
193       "Module::Pluggable": passing a "package" option allows you to place the
194       plugin method in a different package other than your own.
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196   file_regex
197       By default "Module::Pluggable" only looks for .pm files.
198
199       By supplying a new "file_regex" then you can change this behaviour e.g
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201           file_regex => qr/\.plugin$/
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203   include_editor_junk
204       By default "Module::Pluggable" ignores files that look like they were
205       left behind by editors. Currently this means files ending in ~ (~), the
206       extensions .swp or .swo, or files beginning with .#.
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208       Setting "include_editor_junk" changes "Module::Pluggable" so it does
209       not ignore any files it finds.
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METHODs

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

220       This does everything I need and I can't really think of any other
221       features I want to add. Famous last words of course
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223       Recently tried fixed to find inner packages and to make it 'just work'
224       with PAR but there are still some issues.
225
226       However suggestions (and patches) are welcome.
227

AUTHOR

229       Simon Wistow <simon@thegestalt.org>
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COPYING

232       Copyright, 2006 Simon Wistow
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234       Distributed under the same terms as Perl itself.
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BUGS

237       None known.
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