iOS NSNotificationCenter Observer未被删除

我在AppDelegate中有以下代码.目的是创建几个观察者,然后调用一些代码.一旦该代码完成,然后发布通知,然后观察者应该删除两个观察者并调用完成处理程序.

我的问题是看来观察员没有像我预期的那样被删除.发布通知,并将NSLog条目写入控制台,因此我知道观察者正在工作.但是,在第二次调用时,NSLog被调用两次,第三次调用三次等.

我的想法是,这与从观察者运行的代码块中的删除有关,但是,我不确定如何解决这个问题(如果这确实是问题所在).

有人可以如此善良地解释我是如何实现这一目标的吗？

谢谢.

-(void) application:(UIApplication *)application performFetchWithCompletionHandler:
(void (^)(UIBackgroundFetchResult))completionHandler {

    [[NSNotificationCenter defaultCenter] addObserverForName:@"fetchDidCompleteNewData" object:nil
                                                     queue:nil usingBlock:^(NSNotification *completed) {

                                                         //Remove Observers
                                                         [[NSNotificationCenter defaultCenter] removeObserver:self
                                                                                                         name:@"fetchDidCompleteNewData"
                                                                                                       object:nil];
                                                         [[NSNotificationCenter defaultCenter] removeObserver:self
                                                                                                         name:@"fetchDidCompleteNoData"
                                                                                                       object:nil];


                                                         // Post completion
                                                         completionHandler(UIBackgroundFetchResultNewData);
                                                         NSLog(@"Background fetch completed... New Data");
                                                     }];

    [[NSNotificationCenter defaultCenter] addObserverForName:@"fetchDidCompleteNoData" object:nil
                                                       queue:nil usingBlock:^(NSNotification *completed) {

                                                           //Remove Observers
                                                           [[NSNotificationCenter defaultCenter] removeObserver:self
                                                                                                           name:@"fetchDidCompleteNoData"
                                                                                                         object:nil];

                                                           [[NSNotificationCenter defaultCenter] removeObserver:self
                                                                                                           name:@"fetchDidCompleteNewData"
                                                                                                         object:nil];

                                                           //post completion
                                                           completionHandler(UIBackgroundFetchResultNoData);
                                                           NSLog(@"Background fetch completed... No New Data");

                                                       }];

    GetDetails *getDetails = [[GetDetails alloc] init];
    [getDetails backgroundRefresh];

}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [[UIApplication sharedApplication] setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];

    return YES;
}

您没有将self注册为对象.此外,当块被addObserverForName压入堆栈时：该方法尚未返回,因此通知为零.

使用块创建一个全局对象,例如

__block __weak id notification;

然后,

notification =  [[NSNotificationCenter defaultCenter] addObserverForName:@"fetchDidCompleteNewData" object:nil queue:nil usingBlock:^(NSNotification *completed) {

   //Remove Observers
   [[NSNotificationCenter defaultCenter] removeObserver:notification];
}];