hasListeners.m

@implementation CalendarManager
{
  bool hasListeners;
}

// Will be called when this module's first listener is added.
-(void)startObserving {
    hasListeners = YES;
}

// Will be called when this module's last listener is removed, or on dealloc.
-(void)stopObserving {
    hasListeners = NO;
}

- (void)sendEvent {
  if (hasListeners) { 
    [self sendEventWithName:@"SomeEvent" body:@{@"body": someBody}];
  }
}