比较CLLocationDistance的两个实例来缩小较小的一个

Question

嗨我的应用程序中有一个mapAnnotations数组。每个注释对象都有一个地址和一个坐标。我正在使用我的位置管理器来查找用户的当前位置，它是一个CLLocationDistance对象。然后，我试图迭代mapAnnotations数组，并将用户的位置与每个注释的位置坐标进行比较，以找到接近用户的位置坐标。 下面是代码：

-(void)locationManager:(CLLocationManager*)_manager 
    didUpdateToLocation:(CLLocation *)newLocation 
    fromLocation:(CLLocation *)oldLocation 
{ 
    self.userLocation = newLocation; 
    NSLog(@"Usser location is: %@", self.userLocation); 
    NSLog(@"USer location latitude = %.4f", self.userLocation.coordinate.latitude); 
    NSLog(@"USer location longitude = %.4f", self.userLocation.coordinate.longitude); 
    if (self.userLocation) 
    { 
     [self.locMgr stopUpdatingLocation]; 
    } 
    [self calculateShortestDistanceBetweenUserAndBiz:self.userLocation]; 
} 

//============================================================================== 
-(void)calculateShortestDistanceBetweenUserAndBiz:(CLLocation *)_userLocation 
{ 
    NSLog(@"Entering %s", __FUNCTION__); 
    for(LocationMapAnnotation *tempAnnot in self.mapAnnotations) 
    { 
     CLLocation *tempLocation = [[CLLocation alloc] initWithLatitude:tempAnnot.coordinate.latitude longitude:tempAnnot.coordinate.longitude]; 
     NSLog(@"tempLocation created %@ ", tempLocation); 
     CLLocationDistance tempDistance = [_userLocation distanceFromLocation: tempLocation]; 
     NSLog(@"tempDistance was calculated at %d", tempDistance); 
     if(!self.shortestDistance) 
     { 
      self.shortestDistance = tempDistance; 
      NSLog(@"Assigned value %d to shortestDistance", self.shortestDistance); 
      continue; 
     } 
     if(self.shortestDistance >= tempDistance) 
     { 
     NSLog(@"Replacing shortest distance value from %d to %d", self.shortestDistance, tempDistance); 
      self.shortestDistance = tempDistance; 
     } 
    } 
} 

的方法效果很好，这里是控制台输出：

Created a new locationmodel 

Usser location is: <+43.47878384, -80.53074371> +/- 1629.00m (speed -1.00 mps/course -1.00) @ 11-05-22 8:58:10 PM Eastern Daylight Time 

USer location latitude = 43.4788 

USer location longitude = -80.5307 

Entering -[locationModel calculateShortestDistanceBetweenUserAndBiz:] 

tempLocation created <+43.69445000, -79.75080000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at 629486151 

Assigned value 629486151 to shortestDistance 

tempLocation created <+43.62192000, -79.52238000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at 209234637 
tempLocation created <+43.59233000, -79.54258000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at -1442027836 
tempLocation created <+43.57980000, -79.61713000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at -680604989 

tempLocation created <+43.55260000, -79.58553000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at -1882725832 
tempLocation created <+43.58191000, -79.71417000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at 947780311 

Replacing shortest distance value from 629486151 to 1089496493 

tempLocation created <+43.65530000, -79.41298000> +/- 0.00m (speed -1.00 mps/course -1.00) 

tempDistance was calculated at 1561068529 

tempLocation created <+43.64854000, -79.38776000> +/- 0.00m (speed -1.00 mps/course -1.00) 
tempDistance was calculated at 466814513 

tempLocation created <+43.47690000, -80.52500000> +/- 0.00m (speed -1.00 mps/course -1.00) 
tempDistance was calculated at -1816387020 
Replacing shortest distance value from 947780311 to 1089489801 
Received memory warning. Level=1 

我的问题是现在的功能正在工作，我试着去理解价值是什么意思？例如，分配给最短距离和远距离的值是巨大的数字，但它们代表什么？我如何知道该功能正常工作。我不明白。我希望能够用最短距离的这个值来这里把我的我的MKMapView，我不会更换下面对应的最短距离是用户的位置cetercoord值线

MKCoordinateRegion preRegion = MKCoordinateRegionMakeWithDistance(centerCoord, 15000, 15000); 

请帮忙。

Answer 1

CLLocationDistance是double的类型，因此您需要使用%f而不是%d（用于整数）。这可能是你看到非常大的无意义数字的原因。

假设shortestDistance也被声明为CLLocationDistance，记录时也是如此。

CLLocationDistance是米，这也是什么MKCoordinateRegionMakeWithDistance预计过去两个参数，因此该行可能是：

MKCoordinateRegion preRegion = MKCoordinateRegionMakeWithDistance 
    (centerCoord, shortestDistance, shortestDistance); 

另一个无关的事情：

您有内存泄漏：你需要释放拨打distanceFromLocation后致电tempLocation。