MapView doesn't show Annotations after adding viewForAnnotations - swift

Question

so I am using MapKit for the first time and I am trying to show annotations with a callout.
The annotations appear but as soon as I add the delegate function viewFor annotation (func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {}) the annotations do not appear anymore. Is there anything I am missing in that function ?
Edit
I forgot to mention that the View Controller is the delegate of MKMapViewDelegate
#objc func addAnnotationOnLongPress(gesture: UILongPressGestureRecognizer) {
if gesture.state == .ended {
let point = gesture.location(in: self.mapView)
let coordinate = self.mapView.convert(point, toCoordinateFrom: self.mapView)
//Now use this coordinate to add annotation on map.
let annotation = MKPointAnnotation()
annotation.coordinate = coordinate
usf.fetchJSON(urlString: usf.setNewLocation(lat: annotation.coordinate.latitude, lon: annotation.coordinate.longitude)) { (data, success) in
if success {
annotation.title = data?.name
annotation.subtitle = "HAa"
} else {
let alertUI = self.usf.createAlertOK(title: "Something went wrong!", message: "Cannot get the current weather! \n Check your connectivity or try again later")
self.present(alertUI, animated: true, completion: nil)
}
}
let previousAnnotations = self.mapView.annotations
if !previousAnnotations.isEmpty{
self.mapView.removeAnnotation(previousAnnotations[0])
}
self.mapView.addAnnotation(annotation)
}
}
func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
if annotation is MKUserLocation {
return nil
}
print("in viewFor annotation") // prints out
let annotationView = MKAnnotationView(annotation: annotation, reuseIdentifier: "TempAnnotationView")
annotationView.canShowCallout = true
annotationView.rightCalloutAccessoryView = UIButton(type: .detailDisclosure)
self.mapView.showAnnotations(mapView.annotations, animated: false)
return annotationView
}

Answer 1

You are instantiating a MKAnnotationView. If you have some custom image, then set the image property of this MKAnnotationView. Or, easier, just use MKPinAnnotationView or MKMarkerAnnotationView instead.
And as Sh_Kahn noted, make sure you create you annotation inside the closure, not after it.

Answer 2

You need
if success {
let annotation = MKPointAnnotation()
annotation.coordinate = coordinate
annotation.title = data?.name
annotation.subtitle = "HAa"
self.mapView.addAnnotation(annotation)
}
The api that gets name is asynchronous so you have to add the filled annotation inside the callback