How to change image to an MKAnnotation with Swift - ios

Question

I have a map with 2 annotations and I want 2 different images to each of them.
I know how to do it with one annotation, but my problem is with two annotations.
Here is my code for one:
func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
let reuseId = "pin"
var anView = mapView.dequeueReusableAnnotationViewWithIdentifier(reuseId)
anView = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseId)
anView!.image = nil;
anView!.image = UIImage(named:"destinationPin")
return anView
}
And If anyone can I'd really appreciate if you explain me what is reuseId.
Thanks in advance

Answer 1

First, when adding the annotations to the map, you'll need to differentiate between them. The easy way is to set the tag value. Then you can branch you logic as follows:
if annotation.tag == 0 {
anView!.image = UIImage(named:"destinationPin")
} else {
anView!.image = UIImage(named:"alternateDestinationPin")
}
Note MKAnnotation has other properties like title and coordinate that can be used to branch your logic.

Answer 2

You can cast them as Optionals.
func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
let reuseId = "pin"
var anView = mapView.dequeueReusableAnnotationViewWithIdentifier(reuseId)
if let annotation1 = anView as? FirstAnnotation {
annotation1.image = UIImage(named: "first.jpg")
} else if let annotation2 = anView as? SecondAnnotation {
annotation2.image = UIImage(named: "second.jpg")
}
return anView
}
This has the added benefit of type-safety and not relying on your own knowledge of what's lying inside a tag. If you have two separate MKAnnotation types, you should really sub-class them as two individual classes.