地理编码和地理反编码

#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>

@interface ViewController : UIViewController<CLLocationManagerDelegate>
{
    CLLocationManager *_locationManager;
    CLGeocoder *_geocoder;
}

@property (strong, nonatomic) IBOutlet UILabel *geocodingResultsLabel;
@property (strong, nonatomic) IBOutlet UIButton *reverseGeocodingButton;
@property (strong, nonatomic) IBOutlet UITextField *addressTextField;

- (IBAction)findCurrentAddress:(id)sender;
- (IBAction)findCoordinateOfAddress:(id)sender;

反向地理编码：

- (IBAction)findCurrentAddress:(id)sender
{
    if([CLLocationManager locationServicesEnabled])
    {
        if(_locationManager==nil)
        {
            _locationManager=[[CLLocationManager alloc] init];
            _locationManager.distanceFilter = 500;
            _locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
            _locationManager.delegate = self;

            // For backward compatibility, set the deprecated purpose property
            // to the same as NSLocationUsageDescription in the Info.plist
            _locationManager.purpose = [[NSBundle mainBundle]
                                         objectForInfoDictionaryKey:@"NSLocationUsageDescription"];
          }

        [_locationManager startUpdatingLocation];
        self.geocodingResultsLabel.text = @"Getting location...";
    }
    else
    {
        self.geocodingResultsLabel.text=@"Location services are unavailable";
    }
}

-(void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    if(error.code == kCLErrorDenied)
    {
        self.geocodingResultsLabel.text = @"Location information denied";
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    // Make sure this is a recent location event
    CLLocation *newLocation = [locations lastObject];
    NSTimeInterval eventInterval = [newLocation.timestamp timeIntervalSinceNow];
    if(abs(eventInterval) < 30.0)
    {
        // Make sure the event is valid
        if (newLocation.horizontalAccuracy < 0)
            return;

        // Instantiate _geocoder if it has not been already
        if (_geocoder == nil)
            _geocoder = [[CLGeocoder alloc] init];

        //Only one geocoding instance per action
        //so stop any previous geocoding actions before starting this one
        if([_geocoder isGeocoding])
            [_geocoder cancelGeocode];

        [_geocoder reverseGeocodeLocation: newLocation
            completionHandler: ^(NSArray* placemarks, NSError* error)
            {
                if([placemarks count] > 0)
                {
                    CLPlacemark *foundPlacemark = [placemarks objectAtIndex:0];
                    self.geocodingResultsLabel.text =
                        [NSString stringWithFormat:@"You are in: %@", foundPlacemark.description];
                }
                else if (error.code == kCLErrorGeocodeCanceled)
                {
                    NSLog(@"Geocoding cancelled");
                }
                else if (error.code == kCLErrorGeocodeFoundNoResult)
                {
                    self.geocodingResultsLabel.text=@"No geocode result found";
                }
                else if (error.code == kCLErrorGeocodeFoundPartialResult)
                {
                    self.geocodingResultsLabel.text=@"Partial geocode result";
                }
                else
                {
                    self.geocodingResultsLabel.text=[NSString stringWithFormat:@"Unknown error: %@", error.description];
                }
            }
         ];

        //Stop updating location until they click the button again
        [manager stopUpdatingLocation];
    }
}

地理编码：

- (IBAction)findCoordinateOfAddress:(id)sender
{
    // Instantiate _geocoder if it has not been already
    if (_geocoder == nil)
        _geocoder = [[CLGeocoder alloc] init];

    NSString *address = self.addressTextField.text;
    [_geocoder geocodeAddressString:address
        completionHandler:^(NSArray *placemarks, NSError *error)
        {
            if ([placemarks count] > 0)
            {
                CLPlacemark *placemark = [placemarks objectAtIndex:0];

                self.geocodingResultsLabel.text = placemark.location.description;
            }
            else if (error.domain == kCLErrorDomain)
            {
                switch (error.code)
                {
                    case kCLErrorDenied:
                        self.geocodingResultsLabel.text = @"Location Services Denied by User";
                        break;
                    case kCLErrorNetwork:
                        self.geocodingResultsLabel.text = @"No Network";
                        break;
                    case kCLErrorGeocodeFoundNoResult:
                        self.geocodingResultsLabel.text = @"No Result Found";
                        break;
                    default:
                        self.geocodingResultsLabel.text = error.localizedDescription;
                        break;
                }
            }
            else
            {
                self.geocodingResultsLabel.text = error.localizedDescription;
            }

        }
     ];
}

实践需要注意：

1、一次只发送一个地理信息编码请求

2、如果用户执行的动作导致对相同的位置进行地理信息编码，那么应该重用结果而不是多次请求相同的位置

3、一分钟内不应该发送一个以上的地理信息编码请求。你应该检查用户在调用另一次地理信息编码请求前位置是否发生了显著移动。

4、如果看不到结果，那么请不要执行地理信息编码请求（比如说，应用程序是否运行在后台）