iOS CLLocation 代码运行顺序

Question

我已经设法使用 GLGeocoder geocodeAddressString 获取了 2 个城市的坐标

从名称中检索到这 2 个城市的坐标后，我想计算它们之间的距离。但是我面临一个问题，因为 CLLocationDistance 在 geocodeAddressString 之前运行。

我如何确保仅在城市位置有之后才计算距离？

请看下面我的代码:

__block CLLocation *depLocation;
__block CLLocation *arrLocation;

CLGeocoder *geocoder = [[CLGeocoder alloc] init];
[geocoder geocodeAddressString:@"Birmingham" completionHandler:^(NSArray* placemarks, NSError* error){
    for (CLPlacemark* aPlacemark in placemarks)
    {

        depLocation = [[CLLocation alloc]
                       initWithLatitude:aPlacemark.location.coordinate.latitude
                       longitude:aPlacemark.location.coordinate.longitude];

    }
}];

CLGeocoder *geocoder2 = [[CLGeocoder alloc] init];
[geocoder2 geocodeAddressString:@"Amritsar" completionHandler:^(NSArray* placemarks2, NSError* error){
    for (CLPlacemark* aPlacemark2 in placemarks2)
    {

        arrLocation = [[CLLocation alloc]
                       initWithLatitude:aPlacemark2.location.coordinate.latitude
                       longitude:aPlacemark2.location.coordinate.longitude];

    }
}];

CLLocationDistance distanceXYZ = [depLocation distanceFromLocation:arrLocation];
NSString *distanceLabel = [NSString stringWithFormat:@"Distance to point %4.0f m.", distanceXYZ];

Answer 1

简单的答案是嵌套所有的完成 block 。复制所有的geoCoder2 的东西并把它放在geocoder 完成 block ，然后复制distanceXYZ 和distanceLabel 到完成geocoder2

block