title: Check if mapView already contains an annotation
body: <p>I have a method of adding secondary nearby annotations (ann2) when I tap on another annotation (ann1). But when I deselect and re-select the exact same annotation (ann1) the ann2 re-creates it self and is getting added again. Is there a way to check if the annotation already exists on the map and if yes then do nothing otherwise add the new annotation. I have already checked this: <a href="https://stackoverflow.com/questions/13970755/restrict-duplicate-annotation-on-mapview">Restrict Duplicate Annotation on MapView</a> but it did not help me.. Any advice is appreciated. This is what I have so far:</p>
  
  <pre><code>    fixedLocationsPin *pin = [[fixedLocationsPin alloc] init];
          pin.title = [NSString stringWithFormat:@"%@",nearestPlace];
          pin.subtitle = pinSubtitle;
          pin.coordinate = CLLocationCoordinate2DMake(newObject.lat, newObject.lon);
  
          for (fixedLocationsPin *pins in mapView.annotations) {
              if (MKMapRectContainsPoint(mapView.visibleMapRect, MKMapPointForCoordinate (pins.coordinate))) {
                  NSLog(@"already in map");
              }else{
                  [mapView addAnnotation:pin];
              }
  </code></pre>
  
  <p>In this case I get the log already on map but I also get the drop animation of the annotation adding to the map. Any ideas?</p>
  
  <p>Thank you in advance..</p>