Objective c 计算两组坐标（NSStrings）之间的距离

我有两组地理坐标，我正试图计算它们之间的距离。我已经做了一些挖掘，但不知道怎么做。我试图获取用户（userLatitude/userLongitude）和地点（placeLatitude/placeLongitude）之间的距离（以英里为单位）。我的坐标存储为NSString，如下所示。有人知道怎么做吗？谢谢大家!

NSString *userLatitude =[(PDCAppDelegate *)[UIApplication sharedApplication].delegate 
getUserLatitude];

NSString *userLongitude =[(PDCAppDelegate *)[UIApplication sharedApplication].delegate 
getUserLongitude];

NSString *placeLatitude = [element1 objectForKey:@"placeLatitude"];

NSString *placeLongitude = [element1 objectForKey:@"placeLongitude"];

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这可能对你有帮助。尝试从您拥有的lat long创建CLLocation

CLLocation* Location1;
CLLocation* Location2;
CLLocationDistance distance = [Location1 distanceFromLocation:Location2];

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从下面可以得到距离

CLLocation *locA = [[CLLocation alloc] initWithLatitude:currentLocation.latitude longitude:currentLocation.longitude];

CLLocation *locB = [[CLLocation alloc] initWithLatitude:[[element1 objectForKey:@"placeLatitude"] doubleValue]  longitude:[[element1 objectForKey:@"placeLongitude"] doubleValue]];

CLLocationDistance currentDistance = [locA distanceFromLocation:locB];