ios - 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 方法中的选择器未被调用。

位置管理器 Object.m 文件(具有标准分派(dispatch)一次和初始化方法的单例)

- (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(一般)

- (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

你的做法不对。为什么添加观察者然后立即将其删除。大多数时候，我们在 viewWillAppear 和 viewWillDisappear 或 viewDidAppear 和 viewDidDisappear 中添加/删除观察者。

它应该是这样的:-

-(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];
}