Get Specific MKAnnotation From Selector

Question

I'm implementing a MKMapView in an app, and have implemented the -mapView: viewForAnnotation: method in order to show dynamically placed pins with callouts on the map. The annotations on the map I'm interested in are defined in a separate class called Annotation that implements MKAnnotation. In the -mapView: viewForAnnotation: method, I need to get the value of the variable which is fed in through the method's annotation variable, which will be an instance of Annotation.

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation {
if ([annotation isKindOfClass:[MKUserLocation class]]) {
    return nil;
}

if ([annotation isKindOfClass:[Annotation class]]) {
    static NSString *identifier = @"RemoteLocation";
    MKPinAnnotationView *annotationView = (MKPinAnnotationView *)[self.mapView dequeueReusableAnnotationViewWithIdentifier:identifier];
    if (annotationView == nil) {
        annotationView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier];
    } else {
        annotationView.annotation = annotation;
    }
    annotationView.enabled = YES;
    //HERE, I NEED TO GET THE VALUE OF annotation's VARIABLE IN ORDER TO ASSIGN THE ANNOTATIONVIEW IMAGE
    //annotationView.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:annotation.senderPhotoURL]]];
    return annotationView;
    }
return nil;
}

The problem is that when I try to get the value of the variable from annotation, which is an instance of Annotation, the variable isn't accessible. What do I need to do to inform the program that annotation is an instance of Annotation, so that the variable is available to read?

Answer 1

Although you have proved that annotation is an Annotation underneath you need to cast it to an actual instance of Annotation, like this:

Annotation* yourAnnotation = (Annotation *)annotation;

Then you can use yourAnnotation as you'd expect.