NAME
Plugin::Tiny - A tiny plugin system for perl
VERSION
version 0.006
SYNOPSIS
use Plugin::Tiny; #in your core
my $ps=Plugin::Tiny->new(); #plugin system
#load plugin_class (and perhaps phase) from your configuration
$ps->register(
phase=>$phase, #optional
plugin=>$plugin_class, #required
role=>$role, #optional
arg1=>$arg1, #optional
arg2=>$arg2, #optional
);
#execute your plugin's methods
my $plugin=$ps->get_plugin ($phase);
$plugin->do_something(@args); DESCRIPTION
Plugin::Tiny is minimalistic plugin system for perl. Each plugin is associated with a keyword (referred to as phase). A limitation of Plugin::Tiny is that each phase can have only one plugin.
ATTRIBUTES
debug
expects a boolean. Prints additional info to STDOUT.
prefix
Optional init argument. You can have the prefix added to all plugin classes you register so save some typing and force plugins in your namespace:
#without prefix
my $ps=Plugin::Tiny->new
$ps->register(plugin='Your::App::Plugin::Example1');
$ps->register(plugin='Your::App::Plugin::Example2');
#with prefix
my $ps=Plugin::Tiny->new ( prefix=>'Your::App::Plugin::' );
$ps->register(plugin='Example1');
$ps->register(plugin='Example2');role
Optional init argument. A default role to be applied to all plugins. Can be overwritten in register.
METHODS
register
Registers a plugin, i.e. loads it and makes a new plugin object. Needs a plugin package name (plugin). Returns the newly created plugin object on success. Confesses on error.
Arguments
plugin
The package name of the plugin. Required. Internally, the value of prefix is prepended to plugin, if set.
phase
A phase asociated with the plugin. Optional. If not specified, Plugin::Tiny uses default_phase to determine the phase.
role
A role that the plugin has to appply. Optional. Specify role=>undef to unset global roles.
force
Force re-registration of a previously used phase. Optional.
Plugin::Tiny confesses if you try to register a phase that has previously been assigned. To overwrite this message make force true.
With force both plugins will be loaded (required, imported) and both return new objects for their respective plugin classes, but after the second plugin is made, the first one can't be accessed anymore through get_plugin.
all other arguments
Remaining arguments are passed down to the plugin constructor. Optional.
$obj=$ps->register(
plugin=>$plugin_class, #required
args=>$more_args, #optional
);
#Plugin::Tiny return result of
#$plugin_class->new (args=>$args);N.B. A side-effect of these arguments is that your plugin cannot use 'phase', 'plugin', 'role', 'force' as named arguments.
register_bundle
Registers a bundle of plugins in no particular order. A bundle is just a hashRef with info needed to issue a series of register calls (see register).
Confesses if a plugin cannot be registered. Otherwise returns $bundle or undef.
sub bundle{
return {
'Store::One' => {
phase => 'Store',
role => undef,
dbfile => $self->core->config->{main}{dbfile},
},
'Scan::Monitor'=> {
core => $self->core
},
};
}
$ps->register_bundle(bundle)If you want to add or remove plugins, use hashref as usual: undef $bundle->{$plugin}; #remove a plugin using package name $bundle->{'My::Plugin'}={phase=>'foo'}; #add another plugin
To facilitate inheritance of your plugins perhaps you put the hashref in a separate sub, so a child bundle can extend or remove plugins from yours.
get_plugin
Returns the plugin object associated with the phase. Returns undef on failure.
$plugin=$ps->get_plugin ($phase);default_phase
Makes a default phase from (the plugin's) class name. Expects a $plugin_class. Returns scalar or undef. If prefix is defined it use tail and removes all '::'. If no prefix is set default_phase returns the last element of the class name:
$ps=Plugin-Tiny->new;
$ps->default_phase(My::Plugin::Long::Example); # returns 'Example'
$ps=Plugin-Tiny->new(prefix=>'My::Plugin::');
$ps->default_phase(My::Plugin::Long::Example); # returns 'LongExample'get_class
returns the plugin's class. A bit like ref $plugin. Not sure what it returns on error. Todo!
$class=$ps->get_class ($plugin);get_phase
returns the plugin's phase. Returns undef on failure. Normally, you should not need this: $phase=$ps->get_phase ($plugin);
SOME THOUGHTS
Your Plugins
Plugin::Tiny requires that your plugins are objects (a package with new). Plugin::Tiny uses Moose internally, but this being perl you are of course free to use whatever object system you like.
package My::Plugin; #a complete plugin that doesn't do very much
use Moose;
sub do_something {
print "Hello World\n";
}
1;Recommendation: First Register Then Do Things
Plugin::Tiny suggests that you first register (load) all your plugins before you actually do something with them. Internal require / use of your packages is deferred until runtime. You can control the order in which plugins are loaded (in the order you call register), but if you manage to load all of them before you do anything, you can forget about order.
You know Plugin::Tiny's phases at compile time, but not which plugins will be loaded.
Recommendation: Require a Plugin Role
You may want to do a plugin role for all you plugins, e.g. to standardize the interface for your plugins. Perhaps to make sure that a specific sub is available in the plugin:
package My::Plugin;
use Moose;
with 'Your::App::Role::Plugin';
#...Plugin Bundles
You can create bundles of plugins if you hand the plugin system down to the (bundleing) plugin. That way, you can load multiple plugins for one phase. You still need unique phases for each plugin:
package My::Core;
use Moose; #optional
has 'plugins'=>(
is=>'ro',
isa=>'Plugin::Tiny',
default=>sub{Plugin::Tiny->new},
);
sub BUILD {
$self->plugins->register(
phase=>'Scan',
plugin=>'PluginBundle',
plugins=>$self->plugins, #plugin system
);
}
package PluginBundle;
use Moose;
has 'plugins'=>(is=>'ro', isa=>'Plugin::Tiny', required=>1);
sub bundle {
{Plugin::One=>{},Plugin::Two=>{}}
}
sub BUILD {
#phase defaults to 'One' and 'Two':
$self->plugins->register_bundle(bundle());
#more or less the same as:
#$self->plugins->register (plugin=>'Plugin::One');
#$self->plugins->register (plugin=>'Plugin::Two');
}
sub start {
my $one=$self->plugins->get('One');
$one->do_something(@args);
}AUTHOR
Maurice Mengel <mauricemengel@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2012 by Maurice Mengel.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.