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<?php |
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/* |
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* The MIT License (MIT) |
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* Copyright © 2017 Marcos Lois Bermudez <[email protected]> |
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* * |
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* Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated |
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* documentation files (the “Software”), to deal in the Software without restriction, including without limitation |
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* the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, |
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* and to permit persons to whom the Software is furnished to do so, subject to the following conditions: |
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* * |
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* The above copyright notice and this permission notice shall be included in all copies or substantial portions |
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* of the Software. |
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* * |
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* THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED |
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* TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF |
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* CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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* DEALINGS IN THE SOFTWARE. |
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*/ |
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namespace TTIC\Laravel\Bridge\Event; |
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use Illuminate\Contracts\Broadcasting\ShouldBroadcast; |
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use Illuminate\Events\Dispatcher; |
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use Symfony\Component\EventDispatcher\Event; |
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use Symfony\Component\EventDispatcher\EventDispatcherInterface; |
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use Symfony\Component\EventDispatcher\EventSubscriberInterface; |
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use Symfony\Component\EventDispatcher\GenericEvent; |
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/** |
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* A event dispatcher that extends Laravel dispatcher and implements |
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* Symfony EventDispatcherInterdace. |
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* |
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* The Laravel events that reach a Synfony listener are wrapped in a |
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* GenericEvent object. |
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* |
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* The Symfony events that reach a Laravel listener are delivered as |
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* is with only one argument with the Event object. |
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* |
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* @package TTIC\Laravel\Bridge\Event |
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* @author Marcos Lois Bermúdez <[email protected]> |
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*/ |
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class EventDispatcher extends Dispatcher implements EventDispatcherInterface |
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{ |
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/** |
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* {@inheritDoc} |
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*/ |
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public function fire($event, $payload = [], $halt = false) |
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{ |
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// When the given "event" is actually an object we will assume it is an event |
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// object and use the class as the event name and this event itself as the |
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// payload to the handler, which makes object based events quite simple. |
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if (is_object($event)) { |
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list($payload, $event) = [[$event], get_class($event)]; |
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} |
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$responses = []; |
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// If an array is not given to us as the payload, we will turn it into one so |
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// we can easily use call_user_func_array on the listeners, passing in the |
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// payload to each of them so that they receive each of these arguments. |
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if (!is_array($payload)) { |
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$payload = [$payload]; |
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} |
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$this->firing[] = $event; |
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if (isset($payload[0]) && $payload[0] instanceof ShouldBroadcast) { |
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$this->broadcastEvent($payload[0]); |
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} |
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foreach ($this->getListeners($event) as $listener) { |
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// Check for a Symfony event listener |
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if ($listener instanceof SymfonyWrappedListener) { |
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// Wrap event if not Symfony one but only one time |
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if (!isset($symfonyEvent)) { |
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$symfonyEvent = (isset($payload[0]) && ($payload[0] instanceof Event)) ? |
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$payload[0] : new GenericEvent('Laravel Wrapped Event', $payload); |
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} |
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$listener($symfonyEvent, $event, $this); |
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if ($symfonyEvent->isPropagationStopped()) { |
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break; |
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} |
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$responses[] = null; |
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continue; |
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} |
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// Laravel listener |
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$response = call_user_func_array($listener, $payload); |
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// If a response is returned from the listener and event halting is enabled |
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// we will just return this response, and not call the rest of the event |
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// listeners. Otherwise we will add the response on the response list. |
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if (!is_null($response) && $halt) { |
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array_pop($this->firing); |
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return $response; |
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} |
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// If a boolean false is returned from a listener, we will stop propagating |
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// the event to any further listeners down in the chain, else we keep on |
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// looping through the listeners and firing every one in our sequence. |
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if ($response === false) { |
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break; |
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} |
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$responses[] = $response; |
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} |
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array_pop($this->firing); |
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return $halt ? null : $responses; |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function addListener($eventName, $listener, $priority = 0) |
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{ |
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// Wrap a Laravel event in a Symfony GenericEvent Object |
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// $this->listen($eventName, function () use ($listener) { |
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// $args = func_get_args(); |
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// |
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// // If not a Symfony Event wrap it |
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// if (!isset($args[0]) || !($args[0] instanceof Event)) { |
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// $event = new GenericEvent(null, $args); |
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// $args = [$event]; |
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// } |
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// $result = call_user_func_array($listener, $args); |
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// |
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// // Check if Symfony listener has stopped the propagation |
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// if (isset($event) && $event->isPropagationStopped()) { |
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// $result = false; |
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// } |
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// |
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// return $result; |
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// }, $priority); |
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$this->listen($eventName, new SymfonyWrappedListener($listener), $priority); |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function dispatch($eventName, Event $event = null) |
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{ |
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if (null === $event) { |
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$event = new Event(); |
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} |
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$this->fire($eventName, $event); |
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return $event; |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function addSubscriber(EventSubscriberInterface $subscriber) |
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{ |
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foreach ($subscriber->getSubscribedEvents() as $eventName => $params) { |
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if (is_string($params)) { |
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$this->addListener($eventName, array($subscriber, $params)); |
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} elseif (is_string($params[0])) { |
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$this->addListener($eventName, array($subscriber, $params[0]), isset($params[1]) ? $params[1] : 0); |
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} else { |
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foreach ($params as $listener) { |
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$this->addListener($eventName, array($subscriber, $listener[0]), isset($listener[1]) ? $listener[1] : 0); |
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} |
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} |
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} |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function removeSubscriber(EventSubscriberInterface $subscriber) |
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{ |
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foreach ($subscriber->getSubscribedEvents() as $eventName => $params) { |
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if (is_array($params) && is_array($params[0])) { |
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foreach ($params as $listener) { |
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$this->removeListener($eventName, array($subscriber, $listener[0])); |
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} |
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} else { |
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$this->removeListener($eventName, array($subscriber, is_string($params) ? $params : $params[0])); |
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} |
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} |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function removeListener($eventName, $listener) |
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{ |
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if (!isset($this->listeners[$eventName])) { |
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return; |
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} |
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foreach ($this->listeners[$eventName] as $priority => $listeners) { |
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foreach ($listeners as $key => $val) { |
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if ($listener == ($val instanceof SymfonyWrappedListener ? $val->getListener() : $val)) { |
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unset($this->listeners[$eventName][$priority][$key], $this->sorted[$eventName]); |
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if (!count($this->listeners[$eventName][$priority])) { |
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unset($this->listeners[$eventName][$priority]); |
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} |
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if (!count($this->listeners[$eventName])) { |
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unset($this->listeners[$eventName]); |
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} |
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return; |
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} |
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} |
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} |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function getListenerPriority($eventName, $listener) |
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{ |
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if (!isset($this->listeners[$eventName])) { |
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return null; |
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} |
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foreach ($this->listeners[$eventName] as $priority => $listeners) { |
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$listeners = array_map(function ($listener) { |
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return $listener instanceof SymfonyWrappedListener ? |
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$listener->getListener() : $listener; |
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}, $listeners); |
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if (false !== in_array($listener, $listeners, true)) { |
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return $priority; |
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} |
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} |
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return null; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function getListeners($eventName = null) |
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{ |
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if (null !== $eventName) { |
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return parent::getListeners($eventName); |
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} |
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foreach ($this->listeners as $eventName => $eventListeners) { |
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if (!isset($this->sorted[$eventName])) { |
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$this->sortListeners($eventName); |
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} |
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} |
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return array_filter($this->sorted); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function hasListeners($eventName = null) |
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{ |
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return parent::hasListeners($eventName); |
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} |
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} |
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.