嘗試使用尚未從自身檢索到的數據后，將調用委托方法didUpdateLocations-Xcode Swift

Question

我有一個NS對象（稱為GoogleSearch），用於獲取用戶的位置數據。 這些是創建的一些全局變量和init函數：

let locationManager = CLLocationManager()
var coordinates: CLLocationCoordinate2D?

override init() {
    super.init()
    print("1")
    DispatchQueue.main.async {
        self.locationManager.delegate = self
        self.locationManager.desiredAccuracy = kCLLocationAccuracyKilometer
        if CLLocationManager.locationServicesEnabled() {
            self.locationManager.startUpdatingLocation()
        }
    }

}

接下來，這是我的委托方法：

extension GoogleSearch: CLLocationManagerDelegate {
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    print("2")
    let userLocation: CLLocation = locations[0] as CLLocation
    self.coordinates = CLLocationCoordinate2D(latitude: userLocation.coordinate.latitude, longitude: userLocation.coordinate.longitude)
}
}

接下來，我嘗試在以后的函數中訪問坐標（在委托方法中設置）：

func searchForPlaces(completion: @escaping ([place])->()) {
    print(coordinates)
}

最后，在實現此NSobject的ViewController中 ，在viewDidLoad中具有以下代碼：

self.googleSearch = GoogleSearch()
    DispatchQueue.main.async {
        self.googleSearch.searchForPlaces(completion: { (places) in
            DispatchQueue.main.async {
                self.places = places
                self.placesCollectionView.reloadData()
            }
        })
    }

問題在於，在searchForPlaces函數中打印坐標將打印nil，因為它是在調用委托方法之前運行的。 我應該在NSObject或ViewController中進行任何更改，以確保可以從searchForPlaces（）訪問坐標嗎？

謝謝。

Answer 1

您可以通過以下方式實現：

class GoogleSearch:NSObject {

  let locationManager = CLLocationManager()
  var coordinates: CLLocationCoordinate2D?
  var completionHandler: ((CLLocationCoordinate2D) -> Void)?

  override init() {
      super.init()
      print("1")

    }

   func searchForPlaces(completion: @escaping (CLLocationCoordinate2D) -> Void) {
     self.completionHandler = completion
     self.locationManager.delegate = self
     self.locationManager.desiredAccuracy = kCLLocationAccuracyKilometer
     if CLLocationManager.locationServicesEnabled() {
        self.locationManager.stopUpdatingLocation()
        self.locationManager.startUpdatingLocation()
     }
   }
}


extension GoogleSearch: CLLocationManagerDelegate {
   func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
     print("2")
     let userLocation: CLLocation = locations[0] as CLLocation
     self.coordinates = CLLocationCoordinate2D(latitude: userLocation.coordinate.latitude, longitude: userLocation.coordinate.longitude)
     self.completionHandler?(self.coordinates!)
    }
}