subscribe method

void subscribe(String key, EventHandler<T> handler)

Adds a handler (callback) that will be executed when this Event is raised using the broadcast method.

See also the + shorcut version.

// Example
counter.onValueChanged.subscribe((args) => print('value changed'));

Implementation

void subscribe(String key, EventHandler<T> handler) {
  if (handler is! EventHandler<T>) {
    throw ArgumentError('a handler must be specified');
  }
  // instantiate handlers if required
  // _handlers ??= new Map<String, EventHandler<T>>();
  if (_handlers.containsKey(key)) print("You've already subscribed using the following key : " + key);

  _handlers[key] = (handler);
}