Why didn't my map annotation move? - iphone

Question

I am implementing a mapView whereby an annotation will be placed when the user search for an address. But somehow, the annotation sometime doesn't move and update to the new coordinate. It's only upon zooming the map, then will it update to the new location. The subtitle did get updated though.
- (void)searchBarSearchButtonClicked:(UISearchBar *)theSearchBar {
SVGeocoder *geocodeRequest = [[SVGeocoder alloc] initWithAddress:searchBar.text inRegion:#"sg"];
[geocodeRequest setDelegate:self];
[geocodeRequest startAsynchronous];
}
- (void)geocoder:(SVGeocoder *)geocoder didFindPlacemark:(SVPlacemark *)placemark {
if (annotation) {
[annotation moveAnnotation:placemark.coordinate];
annotation.subtitle = [NSString
stringWithFormat:#"%#", placemark.formattedAddress];
}
else {
annotation = [[MyAnnotation alloc]
initWithCoordinate:placemark.coordinate
title:#"Tap arrow to use address"
subtitle:[NSString
stringWithFormat:#"%#", placemark.formattedAddress]];
[mapView addAnnotation:annotation];
}
MKCoordinateSpan span;
span.latitudeDelta = .001;
span.longitudeDelta = .001;
MKCoordinateRegion region;
region.center = placemark.coordinate;
region.span = span;
[mapView setRegion:region animated:TRUE];
[searchBar resignFirstResponder];
}

Answer 1

I don't think MKMapView gets notified of changes to an annotation's location. The documentation of MKAnnotation's setCoordinate: says: "Annotations that support dragging should implement this method to update the position of the annotation." so it seems that's the only purpose of this method is for supporting dragging of pins.
Try removing the annotation from the map view before changing its coordinates and then add it back to the map view.

Answer 2

Nothing in your code (that you've shown) tells mapView that the annotation's location has changed. The annotation itself probably can't do it in -moveAnnotation because annotations generally don't know what map or maps they've been added to (nor should they).
The right way to move an annotation is to to remove it from the MKMapView that's using it, update its location, and then add it back to the map. You can't just change the annotation's location after it has been added to the map because the map may very well cache the location or sort the annotation according to its location, and there's no method in MKMapView to tell the map that the location has changed.
I'd change your conditional to something like this:
if (annotation == nil) {
annotation = [[MyAnnotation alloc] init];
annotation.title = #"Tap arrow to use address";
}
[mapView removeAnnotation:annotation];
[annotation moveAnnotation:placemark.coordinate];
annotation.subtitle = placemark.formattedAddress;
[mapView addAnnotation:annotation];
This assumes that it's safe to call -init in place of -initWithCoordinate:title:subtitle:; if not, you'll want to change that.