Listen for all NSNotifications

all_notifications.m

[[NSNotificationCenter defaultCenter] addObserverForName:nil
  object:nil
  queue:nil
  usingBlock:^(NSNotification* notification) {
    NSLog(@"Notification:\n"\
    "name: %@\n"\
    "object: %@\n"\
    "userInfo: %@",
    notification.name,
    notification.object,
    notification.userInfo);
  }];