NSNotification postNotification和addObserver

Question

我正在尝试从位置管理器对象向我的viewController发出通知。它不起作用-- addObserver方法中的选择器没有被调用。

LocationManagerObject.m文件(标准分派一次和init方法的单例)

- (void)setCurrentLocation:(CLLocation *)currentLocation
{
    if (!_location) {
        _location = [[CLLocation alloc] init];
    }
    _location = currentLocation;
    NSNumber *latitude = [NSNumber numberWithDouble:self.location.coordinate.latitude];
    NSNumber *longitude = [NSNumber numberWithDouble:self.location.coordinate.longitude];

    NSLog(@"lat %@ & long %@ in notification section", latitude, longitude);

    NSNotification *notification = [NSNotification notificationWithName:@"myNotification" object:self userInfo:              @{kSetLat: latitude,
        kSetLong: longitude}];


    [[NSNotificationCenter defaultCenter] postNotification:notification];
}

ViewController.m (花园品种)

- (IBAction)welcomeNotification:(UIButton *)sender {
    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
    [center addObserver:self selector:@selector(sendGetRequest:) name:@"myNotification" object:[LPLocationManager sharedManager]];
    [center removeObserver:self];
    NSLog(@"welcomeNotication triggered");

}

Answer 1

你这样做是不对的。为什么要添加观察者，然后立即删除它。大多数情况下，我们在viewWillAppear和viewWillDisappear或viewDidAppear和viewDidDisappear中添加/删除观察者。

应该是这样的：

-(void)viewWillAppear:(BOOL)animated{
  [super viewWillAppear:animated];
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sendGetRequest:) name:@"myNotification" object:nil];
}

-(void)viewWillDisappear:(BOOL)animated{
  [super viewWillDisappear:animated];
  [[NSNotificationCenter defaultCenter] removeObserver:self name:@"myNotification" object:nil];
}