コアデータを使用したSwift 3でのMKAnnotationsの保存と取り込み

Question

ヒットリストとToDoアプリの徹底的な検索と構築の後、私はCore DataとMKAnnotationsの実装に近づいていません。私はNSFetchedResults、NSUserDefaultsまたは他のナンセンスの使用に関するあらゆる種類の提案を見てきました。私は、ピンの場所の保存を実装する方法を知りたいし、CoreDataからそれを取得したいと思います。以下は私の無駄な試みです。

class ViewController: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate { 

    var locationManager: CLLocationManager! 
    var storedLocations: [StoredLocations]! = [] 

    @IBOutlet weak var mapView: MKMapView! 
    @IBOutlet weak var markSpot: UIBarButtonItem! 
    @IBOutlet weak var segmentedControl: UISegmentedControl! 

    // Part of the Fail 
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     navigationController?.isToolbarHidden = false 

     locationManager = CLLocationManager() 
     locationManager.requestWhenInUseAuthorization() 

     let trackingButton = MKUserTrackingBarButtonItem(mapView: mapView) 
     let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: self, action: nil) 
     toolbarItems = [trackingButton, flexibleSpace, markSpot] 

     mapView.delegate = self 
     // More Fail 
     mapView.addAnnotation(getData() as! MKAnnotation) 
    } 

     // Miserable Fail.. Again 
     func getData() { 
      do { 
      storedLocations = try context.fetch(StoredLocations.fetchRequest()) 
      } 
      catch { 
       print("Fetching Failed") 
      } 

     } 

    @IBAction func markSpotPressed(_ sender: Any) { 
     let annotation = MKPointAnnotation() 
     let userLatitude = mapView.userLocation.coordinate.latitude 
     let userLongitude = mapView.userLocation.coordinate.longitude 
     annotation.coordinate = CLLocationCoordinate2D(latitude: userLatitude, longitude: userLongitude) 
     annotation.title = "Dropped Pin" 
     mapView.addAnnotation(annotation) 

    // Another Part of the Fail 
     let newPin = StoredLocations(context: context) 
     newPin.latitude = userLatitude 
     newPin.longitude = userLongitude 
     (UIApplication.shared.delegate as! AppDelegate).saveContext() 

    } 

Answer 1

あなたgetData()関数は何も返さない、そしてそれがなかった場合でも、あなたは、複数の格納されたオブジェクトを持っているかもしれないので、それは、MKAnnotationを返却したいとは思わないでしょう。 MKAnnotation

override func viewDidLoad() { 
    super.viewDidLoad() 

    navigationController?.isToolbarHidden = false 

    locationManager = CLLocationManager() 
    locationManager.requestWhenInUseAuthorization() 

    let trackingButton = MKUserTrackingBarButtonItem(mapView: mapView) 
    let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: self, action: nil) 
    toolbarItems = [trackingButton, flexibleSpace, markSpot] 

    mapView.delegate = self 

    if let annotations = getData() { 
     mapView.addAnnotations(annotations) 
    } 
} 

func getData() -> [MKAnnotation]? { 

    do { 
     storedLocations = try context.fetch(StoredLocations.fetchRequest()) 
     var annotations = [MKAnnotation]() 
     for storedLocation in storedLocations { 
      let newAnnotation = MKPointAnnotation() 
      newAnnotation.coordinate.latitude = storedLocation.userLatitude 
      newAnnotation.coordinate.longitude = storedLocation.userLongitude 
      annotations.append(newAnnotation) 
     } 
     return annotations 
    } 
    catch { 
     print("Fetching Failed") 
    } 
    return nil 
}