地理编码位置数据

geocoder对象是用网络服务把经纬度坐标和用户熟悉的地标相互转换.地标是一个数据集合,包括街道,城市,州/省和国家等信息.
因为地geocoder是依赖于网络.

用CLGeocoder来获取地标信息

使用CLGeocoder来开始反向地理编码的请求,创建这个类的实例并调用reverseGeocodeLocation:completionHandler:方法.这个对象会开始异步的反向地理编码请求,并且把结果在completionHandler:里返回.

@implementation MyGeocoderViewController (CustomGeocodingAdditions)
- (void)geocodeLocation:(CLLocation*)location forAnnotation:(MapLocation*)annotation
{
    if (!geocoder)
        geocoder = [[CLGeocoder alloc] init];
 
    [geocoder reverseGeocodeLocation:location completionHandler:
        ^(NSArray* placemarks, NSError* error){
            if ([placemarks count] > 0)
            {
                annotation.placemark = [placemarks objectAtIndex:0];
 
                // Add a More Info button to the annotation's view.
                MKPinAnnotationView* view = (MKPinAnnotationView*)[map viewForAnnotation:annotation];
                if (view && (view.rightCalloutAccessoryView == nil))
                {
                    view.canShowCallout = YES;
                    view.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
                }
            }
    }];
}
@end

将地名转换成坐标

[geocoder geocodeAddressString:@"1 Infinite Loop"
     completionHandler:^(NSArray* placemarks, NSError* error){
         for (CLPlacemark* aPlacemark in placemarks)
         {
             // Process the placemark.
         }
}];