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Plugin-Tiny-0.012
River stage zero No dependents
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/ Plugin::Tiny

NAME

Plugin::Tiny - A tiny plugin system for perl

VERSION

version 0.012

SYNOPSIS

  #a complete 'Hello World' plugin
  package My::Plugin; 
  use Moose; #optional; required is an object with new as constructor
  sub do_something { print "Hello World @_\n" }
  1;


  #in your core
  use Plugin::Tiny;           
  my $ps=Plugin::Tiny->new(); #plugin system
  
  #load My::Plugin: require, import, return My::Plugin->new(@_)
  my $plugin=$ps->register(plugin=>'My::Plugin');


  #elsewhere in core: 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.

Plugin::Tiny calls itself tiny because it doesn't attempt to solve all problems plugin systems could solve, because it consists of one smallish package, and it doesn't depend on a whole lot.

ATTRIBUTES

debug

Optional. Expects a boolean. Prints additional info to STDOUT.

prefix

Optional. 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. One or more roles that all plugins have to be able to do. Can be overwritten in register.

    role=>['Role::One', Role::Two]      #either as ArrayRef 
    role=>'Role::One'                   #or a scalar

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. Remaining arguments are passed down to the plugin constructor:

    $obj=$ps->register(
        plugin=>$plugin_class,   #required
        args=>$more_args,        #optional
    ); #returns result of $plugin_class->new (args=>$args);

N.B. Your plugin cannot use 'phase', 'plugin', 'role', 'force' as named arguments.

plugin

The package name of the plugin. Required. Internally, the value of prefix is prepended to plugin.

phase

A phase asociated with the plugin. Optional. If not specified, Plugin::Tiny uses default_phase to determine the phase.

role

One or more roles that the plugin has to appply. Optional. Specify role=>undef to unset global roles. Currently, you can't mix global roles (defined via new) with local roles (defined via register).

    role=>'Single::Role' #or
    role=>['Role::One','Role:Two']
    role=>undef #unset global roles
force

Force re-registration of a previously used phase. Optional.

Normally, 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 cannot be accessed anymore through get_plugin.

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.

  my $plugin=$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:

    my $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 (package name). Expects plugin (not its package name). Croaks on error.

  my $class=$ps->get_class ($plugin);

get_phase

returns the plugin's phase. Expects plugin (not its package name). Returns undef on failure. (You will not normally need get_phase, because typically your code knows the phases.)

  my $phase=$ps->get_phase ($plugin);

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 may 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 pass the plugin system to the (bundling) plugin. That way you can load multiple plugins for one phase. You still need unique phases for each plugin:

  package My::Core;
  use Moose; 
  has 'plugin_system'=>(
    is=>'ro',
    isa=>'Plugin::Tiny', 
    default=>sub{Plugin::Tiny->new},
  );

  sub BUILD {
    $self->plugins->register(
      plugin=>'PluginBundle', 
      phase=>'Bundle',
      plugin_system=>$self->plugins, 
    );
  }

  #elsewhere in core
  my $b=$self->plugin_system->get_plugin ('Bundle');  
  $b->start();


  package PluginBundle;
  use Moose;
  has 'plugin_system'=>(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);  
  }

CONTRIBUTORS

Thanks to Toby Inkster for making Plugin::Tiny tinier.

SEE ALSO

Object::Pluggable Module::Pluggable MooX::Role::Pluggable MooseX::Object::Pluggable MooseX::Role::Pluggable

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.