CLLocationManager - 致命錯誤：意外地發現零，而解包一個可選值

Question

我有一個CLLocationManager小問題。當我點擊IBAction「addPlace」時，應用程序崩潰。我沒有看到問題，我不明白爲什麼應用程序崩潰。

非常感謝您的回覆。

class Map: UIViewController, CLLocationManagerDelegate { 

    // Outlets 

    @IBOutlet weak var mapView: MKMapView! 
    @IBOutlet weak var BTNAdd: UIButton! 

    // Variables 

    var positionManager = CLLocationManager() 
    var geoCoder : CLGeocoder! 
    var placemark : CLPlacemark! 

    var name: String = "" 
    var address: String = "" 
    var longitude: String = "" 
    var latitude: String = "" 

    // Actions 

    @IBAction func myPosition(sender: AnyObject) { 

     positionManager.delegate = self 
     positionManager.desiredAccuracy = kCLLocationAccuracyBest 
     positionManager.requestWhenInUseAuthorization() 
     positionManager.startUpdatingLocation() 

     mapView.showsUserLocation = true 

    } 

    @IBAction func addPlace(sender: AnyObject) { 

      /////////////////////////////////////// 
      // BUG HERE 
      /////////////////////////////////////// 

      let locality = String(self.placemark.locality) 
      let postalCode = String(self.placemark.postalCode) 
      let administrativeArea = String(self.placemark.administrativeArea) 
      let country = String(self.placemark.country) 

      print(locality + postalCode + administrativeArea + country) 

      /////////////////////////////////////// 
      /////////////////////////////////////// 

    } 

    // Functions 

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) { 

     CLGeocoder().reverseGeocodeLocation(manager.location!, completionHandler: {(placemarks, error)->Void in 

      if let pm = placemarks?.first { 
       self.displayLocationInfo(pm) 
      } 
     }) 

    } 

    func displayLocationInfo(placemark: CLPlacemark?) { 
     if let containsPlacemark = placemark { 

      positionManager.stopUpdatingLocation() 

      let locality = (containsPlacemark.locality != nil) ? containsPlacemark.locality : "" 
      let postalCode = (containsPlacemark.postalCode != nil) ? containsPlacemark.postalCode : "" 
      let administrativeArea = (containsPlacemark.administrativeArea != nil) ? containsPlacemark.administrativeArea : "" 
      let country = (containsPlacemark.country != nil) ? containsPlacemark.country : "" 

     } 

    } 

} 

Answer 1

我添加類變量，並修復我的IBAction爲

var locality: String = "" 
var postalCode: String = "" 
var administrativeArea: String = "" 
var country: String = "" 

@IBAction func addPlace(sender: AnyObject) { 

    let locality = self.locality 
    let postalCode = self.postalCode 
    let administrativeArea = self.administrativeArea 
    let country = self.country 

    print(locality + postalCode + administrativeArea + country) 

} 

Answer 2

你placemark變量聲明爲一個明確的展開可選的，但因爲你得到這個錯誤信息很明顯，有時這個變量將是零。

更改聲明，使之正常可選，然後用if let確保安全的解包和處理錯誤：

var placemark : CLPlacemark? 

@IBAction func addPlace(sender: AnyObject) { 

     if let mark = placemark { 
      let locality = String(self.mark.locality) 
      let postalCode = String(self.mark.postalCode) 
      let administrativeArea = String(self.mark.administrativeArea) 
      let country = String(self.mark.country) 
      print(locality + postalCode + administrativeArea + country) 
     } else { 
      print("placemark was nil") 
     } 

}