title: Swift Annotation Not Placed on MapView because viewForAnnotation not called
body: <p>I am working on an app that places a pin at the users current location as well as places pins based on input from the user for locations. The current location annotation is being placed fine, however when trying to place the user's input coordinates, the annotation is not placed. I have added the annotation properly using map.addAnnotation(annotation) for which annotation.coordinate (for New York) is CLLocationCoordinate2D(latitude: 40.713054, longitude: -74.007227999999998). I found that the viewForAnnotation method is not being called and I think this is the reason why the annotation is not being placed (printing the annotation results in nothing). I have a test app that requests input coordinates and it works in placing the annotation. Also in the test app, printing the annotation in viewForPrints out a value. </p>
  
  <p>Below I have pasted some of the code I think is relevant to the issue. Please comment if you need more.</p>
  
  <pre><code>import UIKit
  import MapKit
  import CoreLocation
  class MapVC: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate {
  
  
  
  @IBOutlet weak var map: MKMapView!
  
  override func viewDidLoad() {
      super.viewDidLoad()
      map.delegate = self
  }
  </code></pre>
  
  <p>This function below takes the values from another class and converts the coordinates into CLLocationCoordinate2D type. As mentioned above, annotation.coordinate (for New York) yields CLLocationCoordinate2D(latitude: 40.713054, longitude: -74.007227999999998), so add works in saving the coordinates.</p>
  
  <pre><code>    func add(newLocation location_one:[String:Any]) {
          let momentaryLat = (location_one["latitude"] as! NSString).doubleValue
          let momentaryLong = (location_one["longitude"] as! NSString).doubleValue
  
          let annotation = MKPointAnnotation()
          annotation.title = location_one["title"] as? String
          annotation.coordinate = CLLocationCoordinate2D(latitude: momentaryLat as CLLocationDegrees, longitude: momentaryLong as CLLocationDegrees)
  
  
  
          map.addAnnotation(annotation) //not sure if this adds the annotation!
  
          self.map.centerCoordinate = annotation.coordinate
      }
  
  
  func mapView(_ map: MKMapView, viewFor annotation: MKAnnotation) -&gt; MKAnnotationView? {
  
      if (annotation is MKUserLocation) {
          return nil
      }
  
      let identifier = "pinAnnotation"
      var annotationView = map.dequeueReusableAnnotationView(withIdentifier: identifier) as? MKPinAnnotationView
  
      if annotationView == nil {
          annotationView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier)
          annotationView?.canShowCallout = true
  
      } else {
          annotationView?.annotation = annotation
  
      }
      map.showAnnotations(map.annotations, animated: true)
      return annotationView
  }
  </code></pre>