Iphone 目标c：如何从定位服务中找到航向（方向）？

我正在做定位服务，希望从定位服务中获得方向，我有所有想要的属性，例如纬度、经度等，但我也想找到方向（方向）

我从CLHeading中找到了一些线索，但仍然无法从CLHeading中获取。我正在使用上面的代码

读取：） 我想你应该用trueHeading

真航向

相对于正北的航向（以度为单位）。（只读） @属性（只读，非原子）CLLocationDirection TrueTHeading

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i、 e.使用

-（void）headingUpdate:（CLHeading*）heading{NSLog（@“This heading%d”，[heading trueHeading]）；}

但问题是headingUpdate未被激发。

 (void)locationUpdate:(CLLocation *)location {
    locationLable.text = [location description];
    CLLocationCoordinate2D coordinate = [location coordinate];
    NSLog(@"This is location   %@",[location description]);
    NSLog(@"Lattitude          =   %@",[NSString stringWithFormat:@"%f", coordinate.latitude]);
    NSLog(@"Langitude          =   %@",[NSString stringWithFormat:@"%f", coordinate.longitude]);
    NSLog(@"Altitude           =   %@",[NSString stringWithFormat:@"%gm", location.altitude]);
    NSLog(@"horizontalAccuracy =   %@",[NSString stringWithFormat:@"%gm", location.horizontalAccuracy]);
    NSLog(@"verticalAccuracy   =   %@",[NSString stringWithFormat:@"%gm", location.verticalAccuracy]);
    NSLog(@"Speed   =   %@",[NSString stringWithFormat:@"%gm", location.speed]);

}


- (void)headingUpdate:(CLHeading *)heading {
    NSLog(@"This is heading   %@",[heading description]);

}

- (void)viewDidLoad {
    locationController = [[MyCLController alloc] init];
    locationController.delegate = self;
    [locationController.locationManager startUpdatingLocation];
    [locationController.locationManager startUpdatingHeading];
}