Highlight or annotate your favorite places on the map view using Swift 3

My demo application is for showing how to use annotations on the map view using Swift 3 (and Xcode 8). It's very simple. When you launch the app, it will show a map and the button "My Annotations". When you tap on the button, the map will navigate to your birth place. Tap on it again, it will show my favorite place called "RUPP". The image below shows how the app looks like when your launch it.

Related classes:

- MKMapView: the map view to be shown on the screen
- MKAnnotation: the info about your location such as coordinate and title
- MKAnnotationView: use it to define how the annotation (your location) looks on the map

1. Create a single application in Xcode 

Suppose you already created the application in Xcode. There should be one View Controller in Interface Builder by default.

2. Update ViewController class as following:

import UIKit

import MapKit

class MapViewAnnotationDemoController: UIViewController, MKMapViewDelegate {

    var mapView: MKMapView!

    var myAnnotationsButton: UIButton!

    private var myAnnotations = [MKAnnotation]()

    private var currentAnnotationIndex: Int = 0

    

    override func loadView() {

        mapView = MKMapView()

        mapView.delegate = self

        view = mapView

    }

    

    override func viewDidLoad() {

        initMyAnnotationsButton()

        initMyAnnotations()

    }

    

    private func initMyAnnotationsButton() {

        myAnnotationsButton = UIButton(frame: CGRect(x: 8, y:40, width: 140, height: 20))

        myAnnotationsButton.setTitle("My Annotations", for: UIControlState.normal)

        myAnnotationsButton.backgroundColor = UIColor.green

        myAnnotationsButton.addTarget(self, action: #selector(showMyAnnotations(_:)), for: UIControlEvents.touchUpInside)

        view.addSubview(myAnnotationsButton)

    }

    

    private func initMyAnnotations() {

        let myBirthPlaceAnnotation = MKPointAnnotation()

        myBirthPlaceAnnotation.title = "My Birth Place (title)"

        myBirthPlaceAnnotation.subtitle = "My Birth Place (subtitle)"

        myBirthPlaceAnnotation.coordinate.latitude = 11.5564

        myBirthPlaceAnnotation.coordinate.longitude = 104.9282

        myAnnotations.append(myBirthPlaceAnnotation)

        

        let ruppAnnotation = MKPointAnnotation()

        ruppAnnotation.title = "RUPP (title)"

        ruppAnnotation.subtitle = "RUPP (subtitle)"

        ruppAnnotation.coordinate.latitude = 11.5690

        ruppAnnotation.coordinate.longitude = 104.8907

        myAnnotations.append(ruppAnnotation)

        

        mapView.addAnnotations(myAnnotations)

    }

    

    func showMyAnnotations(_ sender: UIButton) {

        print("\nshowMyAnnotations() called")

        

        if currentAnnotationIndex == myAnnotations.count - 1 {

            currentAnnotationIndex = 0

        } else {

            currentAnnotationIndex += 1

        }

        

        mapView.showAnnotations([myAnnotations[currentAnnotationIndex]], animated: true)

    }

    

    func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {

        print("\nmapView(viewFor) called")

        

        let pinAnnotationView = MKPinAnnotationView()

        pinAnnotationView.annotation = annotation

        pinAnnotationView.animatesDrop = true

        return pinAnnotationView

    }

}

In initMyAnnotations() method,  we called mapView.addAnnotations(myAnnotations) method. And the addAnnotations() method calls the mapView(_:MKMapView, viewFor: MKAnnotation) method of the map view's delegate to get the instance of MKAnnotationView so the map view will know how to display the annotation. The delegate is the ViewController class in this case cause it extends MKMapViewDelegate and we set mapView.delegate to self.