buonaparte/bnp-lazy-listener

This library allows you to attach Lazy Listeners to a ZF2 EventManager

0.9.1 2014-07-23 22:54 UTC

Requires

• php: >=5.3.3
• zendframework/zend-eventmanager: 2.*
• zendframework/zend-servicemanager: 2.*

Requires (Dev)

• phpunit/phpunit: >=3.7,<4
• satooshi/php-coveralls: dev-master
• squizlabs/php_codesniffer: 1.4.*

BSD-3-Clause

• Denis Mostovoi

• eventmanager
• zf2
• lazy

README

This library allows you to attach Lazy Listeners to a ZF2 EventManager.

Installation

Setup

1. Add this project to your composer.json:

   "require": {
       "buonaparte/bnp-lazy-listener": "0.9.*"
   }

2. Now tell composer to download BnpServiceDefinition by running the command:

   $ php composer.phar update

!!! Notice this is not a Module, so you do not have to enable it in a ZF2 Application, moreover, you can use it with the EventManager decoupled component.

LazyListenerAggregate

There are many cases when instantiating a listener aggregate may be too expensive, especially when that listener will be never triggered, LazyListenerAggregate makes it possible to define a factory for your real listener, as well as specifications for which events the future listener is subscribed, LazyListenerAggregate will then instantiate your listener when the first of subscribed is being triggered.

class PlainPhpObjectWithDependencies
{
    // Your Dependencies

    public function __construct($aDependency, $anotherDependency)
    {
        // ...
    }

    public function setExtraDependency($dependency)
    {
        // ...
    }

    public function onFoo(Zend\EventManager\EventInterface $e)
    {
        // do some complex stuff ...
        $e->setParam('foo', 'bar');
    }

    public function onBar(Zend\EventManager\EventInterface $e)
    {
        // do some complex stuff ...
        $e->setParam('bar', 'baz');
    }

    public function onBaz(Zend\EventManager\EventInterface $e)
    {
        // do some complex stuff ...
        $e->setParam('baz', array_merge($e->getParam('baz', array()), array('element'));
    }
}

Now you can attach this PPO to the EventManager:

use Zend\EventManager\EventManager;
use Zend\EventManager\Event;
use BnpLazyListener\LazyListenerAggregate;

$events = new EventManager();

$events->attach(new LazyListenerAggregate(
    function () use ($aDependency, $anotherDependency, $dependency) {
        $listener = new PlainPhpObjectWithDependencies($aDependency, $anotherDependency);
        $listener->setExtraDependency($dependency);

        return $listener;
    },
    array(
        'foo' => 'onFoo',
        'bar' => array('onBar', 1000),
        'baz' => array(
            'onBaz',
            array('onBaz', -99)
        )
    )
));

$events->trigger(new Event('an_event'));

// PlainPhpObjectWithDependencies gets instantiated only now
$events->trigger(new Event('foo'));

We've used \Closure here as factory, LazyListenerAggregate however, accepts any valid callable. As you can already see this does not bring much flexibility, as we wrap statically all our listener dependencies, here is where the second utility listener comes in handy.

ServicesListenerAggregateCollection

This is a ServiceLocatorAware service that is able to aggregate a collection of other ListenerAggregates, from which, the most important one is that described above. All atom listeners are called delegates and can be represented as:

• callable - a callable to invoke to instantiate the delegate, optionally a ServiceLocatorInterface is passed as the only argument
• string (a valid FQ class name implementing Zend\EventManager\ListenerAggregateInterface)
• string (a valid FQ class name implementing Zend\ServiceManager\FactoryInterface)
• Zend\ServiceManager\FactoryInterface instance
• string - not matching a factory class name - will make ServicesListenerAggregateCollection to pull the delegate as a service from currently injected locator
• array - containing 2 elements, the first one - any of above, to use as a lazy factory for the LazyListenerAggregate and the second - an array defining the events being listened to, the second constructor argument for the LazyListenerAggregate

We can now define a bunch of listeners at a time using only a configuration array:

use Zend\ServiceManager\ServiceManager;
use Zend\EventManager\EventManager;
use BnpLazyListener\ServicesListenerAggregateCollection;

$delegates = array(
    'a_listener_aggregate_service',
    'MyApp\Factory\ListenerAggregateFactoryService',
    array(
        'PlainPhpObjectWithDependencies',
        array(
            'foo' => 'onFoo',
            'bar' => array('onBar', 1000),
            'baz' => array(
                'onBaz',
                array('onBaz', -99)
            )
        )
    )
);

$services = new ServiceManager();
// declare your a_listener_aggregate_service and PlainPhpObjectWithDependencies services in the container

$listener = new ServicesListenerAggregateCollection($delegates);
$listener->setServiceLocator($services);

$events = new EventManager();
$events->attach($listener);

$events->trigger(new Event('an_event'));

// PlainPhpObjectWithDependencies gets pulled from the locator only now
$events->trigger(new Event('bar'));