title: Invalid redeclaration of 'mapView(_:viewFor:)'
body: <p>So I'm trying to create an app with custom annotations on the map, and I've been following a tutorial on how to do it. However when I put this code in, its giving me the error</p>
  
  <p>Invalid redeclaration of 'mapView(_:viewFor:)'</p>
  
  <p>Here's the tutorial - <a href="https://www.youtube.com/watch?v=w_aw72i8P_U" rel="nofollow noreferrer">https://www.youtube.com/watch?v=w_aw72i8P_U</a></p>
  
  <pre><code>extension ViewController: MKMapViewDelegate {
      func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -&gt; MKAnnotationView? {
          guard let _annotation = annotation as? MyAnnotation else {return }
          let identifier = "marker"
          var view: MKMarkerAnnotationView
          if let dequeuedView = mapView.dequeueReusableAnnotationView(withIdentifier: identifier) as? MKMarkerAnnotationView {
              dequeuedView.annotation = annotation
              view = dequeuedView
          }
          else
          {
             view = MKMarkerAnnotationView(annotation: annotation, reuseIdentifier: identifier)
              view.canShowCallout = true
              view.calloutOffset = CGPoint(x: -5, y: 5)
              view.rightCalloutAccessoryView = UIButton(type: .detailDisclosure)
          }
          return view
      }
  }
  </code></pre>