旧帖已经回答了这个问题。由于我是Swift的新手，一些声明对我来说真的很混乱，而且一些更新，一些结构也会发生变化。 现在我正在处理从数组记录到地图视图的这个错误。
当我打印这个课时，我得到了结果
class LocationModel: NSObject {
//properties
var name: String?
var address: String?
var latitude: String?
var longitude: String?
//empty constructor
override init()
{
}
//construct with @name, @address, @latitude, and @longitude parameters
init(name: String, address: String, latitude: String, longitude: String) {
self.name = name
self.address = address
self.latitude = latitude
self.longitude = longitude
}
//prints object's current state
override var description: String {
return "Name: \(name), Address: \(address), Latitude: \(latitude), Longitude: \(longitude)"
}
}
but when I used it here, its showing nil.
class DetailViewController : UIViewController {
@IBOutlet weak var mapView: MKMapView!
var selectedLocation : LocationModel?
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
// Create coordinates from location lat/long
var poiCoodinates: CLLocationCoordinate2D = CLLocationCoordinate2D()
poiCoodinates.latitude = CDouble(self.selectedLocation!.latitude!)!
poiCoodinates.longitude = CDouble(self.selectedLocation!.longitude!)!
// Zoom to region
let viewRegion: MKCoordinateRegion = MKCoordinateRegionMakeWithDistance(poiCoodinates, 750, 750)
self.mapView.setRegion(viewRegion, animated: true)
// Plot pin
let pin: MKPointAnnotation = MKPointAnnotation()
pin.coordinate = poiCoodinates
self.mapView.addAnnotation(pin)
//add title to the pin
pin.title = selectedLocation!.name
}
}