advanced-plugin-features.md

Advanced Plugin features

Lazy Subscriber

The decorator Joomla\CMS\Event\LazyServiceSubscriber allows to instantiate the plugin with heavy dependencies only when the event is actually dispatched. The plugin should implement Joomla\Event\SubscriberInterface to be able to use decorator.

Note that the use of the lazy decorator does not make sense when the plugin is subscribed to events that happen regularly, like onAfterInitialise.

Additionally, the interface Joomla\CMS\Event\LazySubscriberInterface allows to use LazyServiceEventListener, however the plugin should implement it on its own.

Example usage of the lazy subscriber decorator for the plugin with heavy dependencies:

Code for plugins/system/example/services/provider.php.

Before, regular plugin service:

return new class () implements ServiceProviderInterface {
  public function register(Container $container)
  {
    $container->set(
        PluginInterface::class,
        function (Container $container) {
            $heavyDependency1 = $container->get(Foo::class);
            $heavyDependency2 = $container->get(Bar::class);
            
            return new ExamplePlugin(
                $container->get(DispatcherInterface::class),
                (array) PluginHelper::getPlugin('system', 'example'),
                $heavyDependency1,
                $heavyDependency2
            );
        }
    );
  }
}

After, plugin service with LazyServiceSubscriber:

return new class () implements ServiceProviderInterface {
  public function register(Container $container)
  {
    $container->set(
        ExamplePlugin::class,
        function (Container $container) {
            $heavyDependency1 = $container->get(Foo::class);
            $heavyDependency2 = $container->get(Bar::class);
            
            return new ExamplePlugin(
                $container->get(DispatcherInterface::class),
                (array) PluginHelper::getPlugin('system', 'example'),
                $heavyDependency1,
                $heavyDependency2
            );
        }
    )->set(
        PluginInterface::class,
        function (Container $container) {
            return new LazyServiceSubscriber($container, ExamplePlugin::class);
        }
    );
  }
}