Lazy Listeners

LazyListenerAggregate

Zend\EventManager\LazyListenerAggregate exists to facilitate attaching a number of listeners as lazy listeners.

Usage

Similar to a LazyListener or LazyEventListener, the LazyListenerAggregate accepts a definition (or, rather, set of definitions) a container-interop instance, and optionall an $env array to its constructor.

Unlike either, however, the definition provided is an array of definitions to use to create LazyEventListener instances; you may also intersperse actual LazyEventListener instances if desired.

As an example, let's assume we have two listeners, My\Application\RouteListener and My\Application\DispatchListener; the first will use its onRoute() method to listen to the route event at priority 100, the second its onDispatch() method to listen to the dispatch event at priority -100.

use My\Application\DispatchListener;
use My\Application\RouteListener;
use Zend\EventManager\LazyListenerAggregate;

$definitions = [
    [
        'listener' => RouteListener::class,
        'method'   => 'onRoute',
        'event'    => 'route',
        'priority' => 100,
    ],
    [
        'listener' => DispatchListener::class,
        'method'   => 'onDispatch',
        'event'    => 'dispatch',
        'priority' => -100,
    ],
];

$aggregate = new LazyListenerAggregate(
    $definitions,
    $container
);
$aggregate->attach($events);

Internally, the LazyListenerAggregate will create LazyEventListener instances, and during its attach() phase use them to attach to the event manager using the event and priority they compose.

Below is a functionally identical example, mixing in a concrete LazyEventListener instance for one listener:

use My\Application\DispatchListener;
use My\Application\RouteListener;
use Zend\EventManager\LazyEventListener;
use Zend\EventManager\LazyListenerAggregate;

$dispatchListener = new LazyEventListener([
    'listener' => DispatchListener::class,
    'method'   => 'onDispatch',
    'event'    => 'dispatch',
    'priority' => -100,
], $container);

$definitions = [
    [
        'listener' => RouteListener::class,
        'method'   => 'onRoute',
        'event'    => 'route',
        'priority' => 100,
    ],
    $dispatchListener,
];

$aggregate = new LazyListenerAggregate(
    $definitions,
    $container
);
$aggregate->attach($events);

Recommendations

We recommend using LazyListenerAggregate when you have listeners you will be pulling from a Dependency Injection Container, but which may not execute on every request; this will help minimize the number of objects pulled from the DIC. As pulling instances from a DIC is often an expensive operation, this can be a healthy performance optimization.