Add event extender (used for domain events) (#2097)

framework/core/src/Extend/Event.php

@@ -0,0 +1,45 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Extend;
+
+use Flarum\Extension\Extension;
+use Illuminate\Contracts\Container\Container;
+use Illuminate\Events\Dispatcher;
+
+class Event implements ExtenderInterface
+{
+    private $listeners = [];
+
+    /**
+     * Add a listener to a domain event dispatched by flarum or a flarum extension.
+     *
+     * The listener can either be:
+     *  - a callback function or
+     *  - the class attribute of a class with a public `handle` method, which accepts an instance of the event as a parameter
+     *
+     * @param string $event
+     * @param callable $listener
+     */
+    public function listen(string $event, $listener)
+    {
+        $this->listeners[] = [$event, $listener];
+
+        return $this;
+    }
+
+    public function extend(Container $container, Extension $extension = null)
+    {
+        $events = $container->make(Dispatcher::class);
+
+        foreach ($this->listeners as $listener) {
+            $events->listen($listener[0], $listener[1]);
+        }
+    }
+}