removeListener method Null safety

void removeListener(
  1. String eventName,
  2. EventCallback callback
)

Unsubscribe from getting any future events from emitter. This mechanism uses event name and callback to unsubscribe from all possible events. eventName - Event name for the subscription. callback - EventCallback used when registering subscription using on function.

Implementation

void removeListener(String eventName, EventCallback callback) {
  if (eventName.trim().isEmpty) {
    throw ArgumentError.notNull('eventName');
  }

  // Check if listeners have the specific event already registered.
  // if so, then check for the callback registration.

  if (_listeners.containsKey(eventName)) {
    var subs = _listeners[eventName]!;
    subs.removeWhere((element) =>
        element.eventName == eventName && element.callback == callback);
  }
}