viewDidLoad 中的方法顺序

Question

我在 viewDidLoad 中有方法，调用方法的顺序似乎很奇怪。

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Get Location
    self.locationManager = [[CLLocationManager alloc] init];
    self.geocoder = [[CLGeocoder alloc] init];
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    if([self.locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)])
    {
        [self.locationManager requestWhenInUseAuthorization];
    }
    [self.locationManager startUpdatingLocation];

    // Retrieve Data
    [self retrieveData];
}

调用viewDidLoad后，调用locationManager之前的retrieveData方法

因为顺序的原因，不应该在 retrieveData 之前调用 locationManager 吗？

我是Objective C的新人，提前感谢您的帮助。

Answer 1

根据您的需要在委托方法中调用您的方法，因此从 ViewDidLoad 中删除 [self retrieveData]; 并添加到 didFailWithError 或 didUpdateLocations 方法中。

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Get Location
    self.locationManager = [[CLLocationManager alloc] init];
    self.geocoder = [[CLGeocoder alloc] init];
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    if([self.locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)])
    {
        [self.locationManager requestWhenInUseAuthorization];
    }
    [self.locationManager startUpdatingLocation];


}


- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
UIAlertView *errorAlert = [[UIAlertView alloc]
                           initWithTitle:@"Error" 
                                 message:@"Failed to Get Your Location"              
                                delegate:nil 
                       cancelButtonTitle:@"OK" 
                      otherButtonTitles:nil];
[errorAlert show];

 // call here 
  [self retrieveData];
}

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{

  // set or stop your location update
  manager = nil;
  [self.locationManager stopUpdatingLocation];
  [manager stopUpdatingLocation];


    CLLocation *newLocation = locations[[locations count] -1];
    CLLocation *currentLocation = newLocation;
    NSString *longitude = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude];
    NSString *latitude = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude];

if (currentLocation != nil) {
   NSLog(@"latitude: %@", latitude);
   NSLog(@"longitude: @"%@", longitude);
}else {
    UIAlertView *errorAlert = [[UIAlertView alloc]
                               initWithTitle:@"Error" message:@"Failed to Get Your Location" 
                                                     delegate:nil 
                                            cancelButtonTitle:@"OK" 
                                            otherButtonTitles:nil];
    [errorAlert show];
}

// call here
[self retrieveData];

}

备注

objective -C is the interpreter , it execute the every in step by step , so or may be your [self retrieveData]; is called in main thread, that is the reason it execute in prior.

viewDidLoad 中的方法顺序

Method orders in viewDidLoad

objective-c

viewdidload

ios