一个简单的使用 NSNotificationCenter 的代码例子

@implementation TestClass    - (void) dealloc  {      // If you don't remove yourself as an observer, the Notification Center      // will continue to try and send notification objects to the deallocated      // object.      [[NSNotificationCenter defaultCenter] removeObserver:self];      [super dealloc];  }    - (id) init  {      self = [super init];      if (!self) return nil;        // Add this instance of TestClass as an observer of the TestNotification.      // We tell the notification center to inform us of "TestNotification"      // notifications using the receiveTestNotification: selector. By      // specifying object:nil, we tell the notification center that we are not      // interested in who posted the notification. If you provided an actual      // object rather than nil, the notification center will only notify you      // when the notification was posted by that particular object.        [[NSNotificationCenter defaultCenter] addObserver:self          selector:@selector(receiveTestNotification:)           name:@"TestNotification"          object:nil];        return self;  }    - (void) receiveTestNotification:(NSNotification *) notification  {      // [notification name] should always be @"TestNotification"      // unless you use this method for observation of other notifications      // as well.        if ([[notification name] isEqualToString:@"TestNotification"])          NSLog (@"Successfully received the test notification!");  }    @end    //... somewhere else in another class ...  - (void) someMethod  {      // All instances of TestClass will be notified      [[NSNotificationCenter defaultCenter]           postNotificationName:@"TestNotification"          object:self];  }