在尝试使用尚未从自身检索的数据后调用Delegate方法didUpdateLocations - Xcode Swift

Question

我有一个NS对象（称为GoogleSearch），用于获取用户的位置数据。这些是创建的一些全局变量和init函数：

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()
        }
    }

}

接下来，这是我的委托方法：

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)
}
}

接下来，我尝试在稍后的函数中访问坐标（在委托方法中设置）：

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

最后，在我实现这个NSobject的ViewController中，我在viewDidLoad中有以下代码：

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

问题是searchForPlaces函数中的打印坐标打印为nil，因为它是在调用委托方法之前运行的。有什么我应该在我的NSObject或者我的ViewController中更改，以确保我可以从searchForPlaces（）访问坐标？

谢谢。

Answer 1

你可以用这种方式实现：

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!)
    }
}