CLLocationDistance：无法获取“getDistanceFrom”去工作

Question

基于视图的应用程序，

.m
- (void)viewDidLoad {
    [super viewDidLoad];
    self.locationManager = [[[CLLocationManager alloc] init] autorelease];
    self.locationManager.delegate = self;
    [[self locationManager] startUpdatingLocation];

}


- (void)locationManager:(CLLocationManager *)manager
    didUpdateToLocation:(CLLocation *)newLocation
           fromLocation:(CLLocation *)oldLocation {

    CurrentLocation = newLocation;
    [locationManager stopUpdatingLocation];
    myActivity.hidden=YES;
    [self reStart];
}


-(void)reStart{

        [self checkAndCreateDatabase];  //Sucess
    [self readFromDatabase]; //Success if I comment the get distance part
    [self sort]; //Success
}


-(void) readFromDatabase {
...

    CLLocationCoordinate2D cord;
    cord.latitude = [[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)] doubleValue];
    cord.longitude =[[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 3)] doubleValue];
    NSDate *today = [NSDate date];
    CLLocation *objectLocation = [[CLLocation alloc] initWithCoordinate:cord altitude:1 horizontalAccuracy:1 verticalAccuracy:-1 timestamp:today];
    CLLocationDistance distance = [objectLocation getDistanceFrom:CurrentLocation]/1000;
    NSLog([NSString stringWithFormat:@"%.0f", distance]);
}

有什么问题吗？

调试器说：

obj_msgSend
0x912e8688  <+0024>  mov    0x20(%edx),%edi

来自数据库的对象： 长：59.291114 纬度：17.816191

Answer 1

使用 distanceFromLocation: 代替

Answer 2

CurrentLocation 是实例变量/属性吗？您无需访问器即可直接设置它，并且不会保留它。如果在 getDistance: 中使用它之前就释放它，将会导致崩溃。

如果它是一个属性，请使用 self.CurrentLocation 来确保它被保留。

而且，建设……

NSLog([NSString stringWithFormat:@"%.0f", distance]);

是有风险和多余的。用……

NSLog(@"%.0f", distance);

代替。