interface EventDispatcherInterface

interface EventDispatcherInterface extends ContractsEventDispatcherInterface {
    
    /**
     * Adds an event listener that listens on the specified events.
     *
     * @param int $priority The higher this value, the earlier an event
     *                      listener will be triggered in the chain (defaults to 0)
     */
    public function addListener(string $eventName, callable $listener, int $priority = 0) : void;
    
    /**
     * Adds an event subscriber.
     *
     * The subscriber is asked for all the events it is
     * interested in and added as a listener for these events.
     */
    public function addSubscriber(EventSubscriberInterface $subscriber) : void;
    
    /**
     * Removes an event listener from the specified events.
     */
    public function removeListener(string $eventName, callable $listener) : void;
    public function removeSubscriber(EventSubscriberInterface $subscriber) : void;
    
    /**
     * Gets the listeners of a specific event or all listeners sorted by descending priority.
     *
     * @return array<callable[]|callable>
     */
    public function getListeners(?string $eventName = null) : array;
    
    /**
     * Gets the listener priority for a specific event.
     *
     * Returns null if the event or the listener does not exist.
     */
    public function getListenerPriority(string $eventName, callable $listener) : ?int;
    
    /**
     * Checks whether an event has any registered listeners.
     */
    public function hasListeners(?string $eventName = null) : bool;

}