Swift different images for Annotation

Question

In the viewForAnnotation delegate method, set the image based on which annotation the method is being called for.

Be sure to do this after the view is dequeued or created (and not only in the if anView == nil part). Otherwise, annotations that use a dequeued view will show the image of the annotation that used the view previously.

With the basic MKPointAnnotation, one crude way to tell annotations apart is by their title but that's not very flexible.

A better approach is to use a custom annotation class that implements the MKAnnotation protocol (an easy way to do that is to subclass MKPointAnnotation) and add whatever properties are needed to help implement the custom logic.

In the custom class, add a property, say imageName, which you can use to customize the image based on the annotation.

This example subclasses MKPointAnnotation:

class CustomPointAnnotation: MKPointAnnotation {
    var imageName: String!
}

Create annotations of type CustomPointAnnotation and set their imageName:

var info1 = CustomPointAnnotation()
info1.coordinate = CLLocationCoordinate2DMake(42, -84)
info1.title = "Info1"
info1.subtitle = "Subtitle"
info1.imageName = "1.png"

var info2 = CustomPointAnnotation()
info2.coordinate = CLLocationCoordinate2DMake(32, -95)
info2.title = "Info2"
info2.subtitle = "Subtitle"
info2.imageName = "2.png"

In viewForAnnotation, use the imageName property to set the view's image:

func mapView(mapView: MKMapView!, viewForAnnotation annotation: MKAnnotation!) -> MKAnnotationView! {
    if !(annotation is CustomPointAnnotation) {
        return nil
    }

    let reuseId = "test"

    var anView = mapView.dequeueReusableAnnotationViewWithIdentifier(reuseId)
    if anView == nil {
        anView = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseId)
        anView.canShowCallout = true
    }
    else {
        anView.annotation = annotation
    }

    //Set annotation-specific properties **AFTER**
    //the view is dequeued or created...

    let cpa = annotation as CustomPointAnnotation
    anView.image = UIImage(named:cpa.imageName)

    return anView
}

iOS Swift Code With Help of Anna and Fabian Boulegue:

import UIKit
import MapKit

class ViewController: UIViewController, MKMapViewDelegate {

    @IBOutlet weak var mapView: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.mapView.delegate = self

        var info1 = CustomPointAnnotation()
        info1.coordinate = CLLocationCoordinate2DMake(26.889281, 75.836042)
        info1.title = "Info1"
        info1.subtitle = "Subtitle"
        info1.imageName = "flag.png"

        var info2 = CustomPointAnnotation()
        info2.coordinate = CLLocationCoordinate2DMake(26.862280, 75.815098)
        info2.title = "Info2"
        info2.subtitle = "Subtitle"
        info2.imageName = "flag.png"

        mapView.addAnnotation(info1)
        mapView.addAnnotation(info2)
    }

    func mapView(mapView: MKMapView!, viewForAnnotation annotation: MKAnnotation!) -> MKAnnotationView! {

        println("delegate called")

        if !(annotation is CustomPointAnnotation) {
            return nil
        }

        let reuseId = "test"

        var anView = mapView.dequeueReusableAnnotationViewWithIdentifier(reuseId)
        if anView == nil {
            anView = MKAnnotationView(annotation: annotation, reuseIdentifier: reuseId)
            anView.canShowCallout = true
        }
        else {
            anView.annotation = annotation
        }

        //Set annotation-specific properties **AFTER**
        //the view is dequeued or created...

        let cpa = annotation as CustomPointAnnotation
        anView.image = UIImage(named:cpa.imageName)

        return anView
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

class CustomPointAnnotation: MKPointAnnotation {
    var imageName: String!
}