ios中传递CGpoint 结果错误

需要发送CGpoint 到主类中。使用了Notification，但是不知在接受端如何从Notification中提取出CGpoint。在log输出的结果是0.0

代码
发送:

 NSValue *pointAsObject =[NSValue valueWithCGPoint:CGPointMake(touchDetectingView.lastTouchPosition.x, touchDetectingView.lastTouchPosition.y)];
  [[NSNotificationCenter defaultCenter] postNotificationName: @"swap" object:pointAsObject];

接收端 Header 文件:

- (void)incomingNotification:(NSNotification *)notification;

接受端 M 文件：

[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(incomingNotification:) name:@"swap" object:nil];

- (void)incomingNotification:(NSNotification *)notification
{
     NSValue *pointAsObject = [[notification userInfo] valueForKey:@"swap"];
    NSLog (@"Successfully received the test notification %f",pointAsObject.CGPointValue.y);
}

请看黑体字，你应该放到userinfo里传递，post的时候，而不是通过object传递

NSValue *pointAsObject =[NSValue valueWithCGPoint:CGPointMake(touchDetectingView.lastTouchPosition.x, touchDetectingView.lastTouchPosition.y)];
NSDictionary *dict = [NSDictionary dictionaryWithObject:pointAsObject
                                                      forKey:@"point"];
[[NSNotificationCenter defaultCenter] postNotificationName: @"swap" object:self userinfo:dict];* ** 

接收并处理消息

- (void)incomingNotification:(NSNotification *)notification
{
          NSValue *pointAsObject = [[notification userInfo] valueForKey:@"point"];
        NSLog (@"Successfully received the test notification %f",pointAsObject.CGPointValue.y);
}