Flag Annotation overlap and interchange to each other - ios

Question

I am facing a problem about show multiple annotation on MKMapView. My question is that, I have three type annotation like as(select_StarFlag, simple_Flag, currentLocation_Flag). all flag are show on map but there are interchange the position between them, when I scroll the map, some Flag overlap each other. I am using following code
func mapView(mapView: MKMapView!, viewForAnnotation annotation: MKAnnotation!) -> MKAnnotationView! {
if (annotation.isKindOfClass(MKUserLocation)) {
//if annotation is not an MKPointAnnotation (eg. MKUserLocation),
//return nil so map view draws"Blue Dot" for standard user location
return nil
}
if (annotation.isKindOfClass(MKPointAnnotation)){
let reuseId = "test"
var anView = mapView.dequeueReusableAnnotationViewWithIdentifier(reuseId) as MKAnnotationView!
if (anView == nil) {
anView = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseId)
anView.canShowCallout = true
var data = Double(annotation.coordinate.latitude)
var data1 = Double(annotation.coordinate.longitude)
var flag = Bool(false)
for geoData in ysDataBaseGeolocationArray{
var geolocationlat = Double()
var geolocationlong = Double()
geolocationlat = Double(geoData.objectAtIndex(0) as NSNumber)
geolocationlong = Double(geoData.objectAtIndex(1) as NSNumber)
if data == geolocationlat && data1 == geolocationlong {
println(geolocationlat)
println(geolocationlong)
flag = true
break
}
}
if flag {
anView.image = UIImage(named:"select_StarFlag")
}
else if data == Double(ysLatitude) && data1 == Double(ysLongitude){
if ysValueFlag != false{
anView.image = UIImage(named:"currentLocation_Flag")
}else {
anView.image = UIImage(named:"simple_Flag")
}
}
else {
anView.image = UIImage(named:"simple_Flag")
}
}
else {
//we are re-using a view, update its annotation reference..
anView.canShowCallout = true
anView.annotation = annotation
}
return anView
}
return nil
}