maxkaemmerer/events

Description:

This library offers interfaces and implementations for a simple event, event-subscriber, event-courier structure.

This is of course not an original idea, but my preferred and fairly simple implementation.

The code is fully tested, I however do not take responsibility for use in production.

Use at your own risk.

Installation:

composer require maxkaemmerer/events

Usage:

Generally you don't want to subscribe each EventSubscriber by hand. You might want to use dependency injection via a container or service-manager.

(An example for the Symfony Framework would be using a CompilerPass)

You would also want to inject the EventCourier itself via dependency injection wherever you need it.

Feel free to create your own implementations of EventCourier, Subscription and Payload if you require something more advanced.

Subscribe an EventSubscriber:

Subscribe an EventSubscriber to the EventCourier. The EventSubscriber's subscription() method returns a Subscription, which contains the name of the Event that the EventSubscriber subscribes to and the priority at which it wants to be notified.

(The higher the priority, the earlier the EventSubscriber get notified of the Event, assuming there are other EventSubscribers with lower priority.)

Best practice would be using the fully qualified class name of the event. MyEvent::class

The EventSubscriber::on($event) method is where your actual domain logic happens.

Feel free to inject services, a container, or whatever else you need, into your EventSubscribers.

$courier = new SimpleEventCourier();


$courier->subscribe(new class implements EventSubscriber
{

    /**
     * @param Event $event
     */
    public function on(Event $event): void
    {
        echo 'Notify Shipping!'  . PHP_EOL;
    }

    /**
     * @return EventSubscription
     */
    public function subscription(): EventSubscription
    {
        return Subscription::fromEventNameAndPriority('PaymentReceived', 50);
    }
});

Dispatch an Event:

Dispatching an Event causes the EventCourier to notify all EventSubscribers, who's Subscription::event() method matches the Event's name, specified by Event:name(), and calls their EventSubscriber::on($event) method in order of priority.

IMPORTANT: EventSubscriber's and the EventCourier never return anything.

...

// The EventSubscriber was subscribed


echo 'Payment received.'  . PHP_EOL;
$courier->dispatch(new class implements Event
{
    public function payload(): EventPayload
    {
        // the payload should of course be built or set in the constructor
        return Payload::fromArray(['price' => '99.99€', 'method' => 'creditCard', 'timestamp' => '12345678']);
    }

    public function name(): string
    {
        // best practice would be using the fully qualified class name MyEvent::class
        return 'PaymentReceived';
    }
});

Result:

Payment received.
Notify Shipping!

Full Example:

<?php

require_once __DIR__ . '/vendor/autoload.php';

use MaxKaemmerer\Events\Event;
use MaxKaemmerer\Events\EventPayload;
use MaxKaemmerer\Events\EventSubscriber;
use MaxKaemmerer\Events\EventSubscription;
use MaxKaemmerer\Events\Implementations\Payload;
use MaxKaemmerer\Events\Implementations\SimpleEventCourier;
use MaxKaemmerer\Events\Implementations\Subscription;

$courier = new SimpleEventCourier();


$courier->subscribe(new class implements EventSubscriber
{

    /**
     * @param Event $event
     */
    public function on(Event $event): void
    {
        echo 'Notify Shipping!' . PHP_EOL;
    }

    /**
     * @return EventSubscription
     */
    public function subscription(): EventSubscription
    {
        return Subscription::fromEventNameAndPriority('PaymentReceived', 50);
    }
});


$courier->subscribe(new class implements EventSubscriber
{
    /**
     * @param Event $event
     */
    public function on(Event $event): void
    {
        echo 'Send Receipt! Payed: ' . $event->payload()->get('price') . PHP_EOL;
    }

    /**
     * @return EventSubscription
     */
    public function subscription(): EventSubscription
    {
        return Subscription::fromEventNameAndPriority('PaymentReceived', 60);
    }
});


echo 'Payment received.' . PHP_EOL;
$courier->dispatch(new class implements Event
{
    public function payload(): EventPayload
    {
        // the payload should of course be built or set in the constructor
        return Payload::fromArray(['price' => '99.99€', 'method' => 'creditCard', 'timestamp' => '12345678']);
    }

    public function name(): string
    {
        // best practice would be using the fully qualified class name MyEvent::class
        return 'PaymentReceived';
    }
});

Result:

Payment received.
Send Receipt! Payed: 99.99€
Notify Shipping!

Send Receipt! Payed: 99.99€ gets echoed first since the corresponding EventSubscriber's Subscription::priority() is higher.