How to identify if MKPointAnnotation has been pressed in Swift? - ios

Question

Using a for loop I have stored a unique URL in each annotation using a tag create in a class named CustomPointAnnotation. I am trying to print out the URL of the annotation that has been pressed. The problem is my output console in Xcode prints nothing when I click on an annotation.
I tried to follow this guide: How to identify when an annotation is pressed which one it is
I replicated all the code but it is not detecting if the annotation was clicked.
How do I know if the annotation is clicked?
Here is the CustomPointAnnotation.
class CustomPointAnnotation: MKPointAnnotation {
var tag: String!
}
I declared the variable tag so I can store a unique variable for each annoation.
My ViewController class:
In the ViewController class there is a loop which iterates through my Firebase Database JSON files:
func displayCordinates() {
ref = Database.database().reference()
let storageRef = ref.child("waterfountains")
storageRef.observeSingleEvent(of: .value, with: { snapshot in
for child in snapshot.children.allObjects as! [DataSnapshot] {
let annotation = CustomPointAnnotation()
let dict = child.value as? [String : AnyObject] ?? [:]
annotation.title = "Water Fountain"
annotation.tag = dict["url"] as? String
annotation.coordinate = CLLocationCoordinate2D(latitude: dict["lat"] as! Double, longitude: dict["long"] as! Double)
self.mapView.addAnnotation(annotation)
}
})
}
The annotations are displayed by calling the functions in viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
displayCordinates()
}
A function which should detect if an annotation has been clicked:
func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView) {
if let annotation = view.annotation as? CustomPointAnnotation {
print(annotation.tag!)
}
}
Thank you for helping.

Answer 1

mapView:didSelect: is a MKMapViewDelegate method. If you do not set mapView.delegate = self on your ViewController this function will never get triggered.
Typically it would get set in ViewDidLoad. before performing any other operations with the mapView. Changing your ViewDidLoad to look like
override func viewDidLoad() {
super.viewDidLoad()
self.mapView.delegate = self
displayCordinates()
}
should fix your issue. For more information on the protocol/delegate design pattern all over the apple frameworks, I suggest this swift article from the Swift Programming Guide.
More specifically to your case, check out all the other functionality/control you can bring with your implementation of MKMapView on your ViewController by checkout out the apple docs on MKMapViewDelegate. This will cover things like monitoring when the map finishes loading, when it fails, when the user's location is updated, and more things you may want to increase the functionality of your app and provide a great user experience.