问没有已知的选择器“JSONValue”实例方法

EN

- (CLLocationCoordinate2D) geoCodeUsingAddress:(NSString *)address
{
  double latitude = 0.0;
  double longitude = 0.0;

  NSString *esc_addr =  [address stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
  NSString *req = [NSString stringWithFormat:@"http://maps.google.com/maps/api/geocode/json?sensor=false&address=%@", esc_addr];

   NSDictionary *googleResponse = [[NSString stringWithContentsOfURL: [NSURL URLWithString: req] encoding: NSUTF8StringEncoding error: NULL] JSONValue];

  NSDictionary    *resultsDict = [googleResponse valueForKey:  @"results"];   // get the results dictionary
  NSDictionary   *geometryDict = [resultsDict valueForKey: @"geometry"];   // geometry dictionary within the  results dictionary
  NSDictionary   *locationDict = [geometryDict valueForKey: @"location"];   // location dictionary within the geometry dictionary

  NSArray *latArray = [locationDict valueForKey: @"lat"];
   NSString *latString = [latArray lastObject];     // (one element) array entries provided by the json parser

  NSArray *lngArray = [locationDict valueForKey: @"lng"];
  NSString *lngString = [lngArray lastObject];     // (one element) array entries provided by the json parser

 CLLocationCoordinate2D location;
 location.latitude = [latString doubleValue];// latitude;
 location.longitude = [lngString doubleValue]; //longitude;

  return location;
}

NSDictionary *googleResponse = [[NSString stringWithContentsOfURL: [NSURL URLWithString: req] encoding: NSUTF8StringEncoding error: NULL] JSONValue];