Method registerListeners

/**
 * Registers legacy Listeners to the Dispatcher, emulating how plugins worked under Joomla! 3.x and below.
 *
 * By default, this method will look for all public methods whose name starts with "on". It will register
 * lambda functions (closures) which try to unwrap the arguments of the dispatched Event into method call
 * arguments and call your on<Something> method. The result will be passed back to the Event into its 'result'
 * argument.
 *
 * This method additionally supports Joomla\Event\SubscriberInterface and plugins implementing this will be
 * registered to the dispatcher as a subscriber.
 *
 * @return  void
 *
 * @since   4.0.0
 */
public function registerListeners()
{
    // Plugins which are SubscriberInterface implementations are handled without legacy layer support
    if ($this instanceof SubscriberInterface) {
        $this->getDispatcher()->addSubscriber($this);
        return;
    }
    $reflectedObject = new \ReflectionObject($this);
    $methods = $reflectedObject->getMethods(\ReflectionMethod::IS_PUBLIC);
    /** @var \ReflectionMethod $method */
    foreach ($methods as $method) {
        if (substr($method->name, 0, 2) !== 'on') {
            continue;
        }
        // Save time if I'm not to detect legacy listeners
        if (!$this->allowLegacyListeners) {
            $this->registerListener($method->name);
            continue;
        }
        /** @var \ReflectionParameter[] $parameters */
        $parameters = $method->getParameters();
        // If the parameter count is not 1 it is by definition a legacy listener
        if (\count($parameters) !== 1) {
            $this->registerLegacyListener($method->name);
            continue;
        }
        /** @var \ReflectionParameter $param */
        $param = array_shift($parameters);
        $paramName = $param->getName();
        // No type hint / type hint class not an event or parameter name is not "event"? It's a legacy listener.
        if ($paramName !== 'event' || !$this->parameterImplementsEventInterface($param)) {
            $this->registerLegacyListener($method->name);
            continue;
        }
        // Everything checks out, this is a proper listener.
        $this->registerListener($method->name);
    }
}