title: display route on iOS 7 maps: addOverlay has no effect
body: <p>i want display a point to point route inside my mapView, i use this code for create the route:</p>
  
  <pre><code>- (IBAction)backToYourCar {
      MKPlacemark *sourcePlacemark = [[MKPlacemark alloc] initWithCoordinate:self.annotationForCar.coordinate addressDictionary:nil];
      NSLog(@"coordiante : locationIniziale %f", sourcePlacemark.coordinate.latitude);
      MKMapItem *carPosition = [[MKMapItem alloc] initWithPlacemark:sourcePlacemark];
      MKMapItem *actualPosition = [MKMapItem mapItemForCurrentLocation];
      NSLog(@"coordiante : source %f, ActualPosition %f", carPosition.placemark.coordinate.latitude ,actualPosition.placemark.coordinate.latitude);
      MKDirectionsRequest *request = [[MKDirectionsRequest alloc] init];
      request.source = actualPosition;
      request.destination = carPosition;
      request.requestsAlternateRoutes = YES;
  
      MKDirections *directions = [[MKDirections alloc] initWithRequest:request];
      [directions calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse *response, NSError *error) {
          if (error) {
              NSLog(@"Error : %@", error);
          }
          else {
              [self showDirections:response]; //response is provided by the CompletionHandler
          }
      }];
  }
  </code></pre>
  
  <p>and this for show the route on the map:</p>
  
  <pre><code>- (void)showDirections:(MKDirectionsResponse *)response
  {
      for (MKRoute *route in response.routes) {
          [self.mapView addOverlay:route.polyline level:MKOverlayLevelAboveRoads];
      }
  }
  </code></pre>
  
  <p>actually this code does nothing.</p>
  
  <p>if i try to print the the distance of route i get the correct value:</p>
  
  <pre><code>route distance: 1910.000000
  </code></pre>
  
  <p>then the route is right, but i can't understand why it doesn't appear on the map!</p>
  
  <p>Any suggestions?</p>