Event listeners should be lambda friendly #236
Description
Currently it's not possible to pass lambdas as event listeners
void EventDispatcher::addEventListener(const std::string& type, EventListener* listener)
You enforce a virtual base type and also force to pass by pointer. Both of these make it impossible to use lambdas. This makes the code much more noisy forcing users to create classes instead of simple callbacks. Instead of a base class
struct EventListener {
virtual void onEvent(Event& event) = 0;
virtual ~EventListener() = default;
};It would be better simply to define
using EventListener = std::function<void(Event&event)>;and pass and store the callback by value. The problem then becomes how to remove the event. Easy is to use a std::shared_ptr with and return it. So we end up with
std::shared_ptr<EventListenerHandle> addEventListener(std::function<void(Event&event)>);The user then hangs onto the EventListenerHandle till they don't need it anymore. As soon as the last copy of this goes out of scope then the listener will be removed. I know you want to make this like threejs but c++ is different and you should take advantage of RAII lifetimes and lambdas.
appModel.listenerSubscription = mesh.addEventListener(
[](Event & event){ std::cout << "my mesh was clicked" << std::endl; }
);