iphone - iOS5 CLGeocoder

Question

我正在为 IOS5 开发一个 iPhone 应用程序。我目前正在使用位于 CoreLocation 框架内的 CLGeocoder 类。我无法弄清楚完成处理程序 block 是否在最后调用，在地理编码发生之后或同时调用。

我只知道完成处理程序 block 是在主线程上运行的。有谁知道完成处理程序 block 是在地理编码完成时运行还是在地理编码器在另一个线程上执行时完成手头任务的代码？

Answer 1

完成处理程序在地理编码器完成地理编码后运行。换句话说，它在地理编码任务完成时运行。它不是为了在地理编码器运行时完成一些其他任务。

完成处理程序包含地标和错误。如果地理编码成功，您将获得一个地标数组。否则，您会收到错误消息。

文档注释:

This method submits the specified location data to the geocoding server asynchronously and returns. Your completion handler block will be executed on the main thread. After initiating a forward-geocoding request, do not attempt to initiate another forward- or reverse-geocoding request.

Geocoding requests are rate-limited for each app, so making too many requests in a short period of time may cause some of the requests to fail. When the maximum rate is exceeded, the geocoder passes an error object with the value kCLErrorNetwork to your completion handler.

@interface MyGeocoderViewController ()

@property (nonatomic, strong) CLGeocoder *geocoder;

@end

@implementation MyGeocoderViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
   
    // Create a geocoder and save it for later.
    self.geocoder = [[CLGeocoder alloc] init];
}
- (void)geocodeAddress:(NSString *)addressString
{
    // perform geocode
    [geocoder geocodeAddressString:addressString
        completionHandler:^(NSArray *placemarks, NSError *error) {

        if ((placemarks != nil) && (placemarks.count > 0)) {
            NSLog(@"Placemark: %@", [placemarks objectAtIndex:0]);
        }
        // Should also check for an error and display it
        else {
            UIAlertView *alert = [[UIAlertView alloc] init];
            alert.title = @"No places were found.";
            [alert addButtonWithTitle:@"OK"];
            [alert show];
        }
    }];
}

@end