在 class 中调用后委托 return nil

Question

我正在使用此 class 获取位置并将其与委托一起发送到另一个视图控制器，但委托在调用时返回 nil。我的 class:

protocol LocationUpdateProtocol {
    func locationDidUpdateToLocation(location : CLLocation)
}
/// Notification on update of location. UserInfo contains CLLocation for key "location"
let kLocationDidChangeNotification = "LocationDidChangeNotification"
class LocationServiceHelper:NSObject,CLLocationManagerDelegate {

    static let sharedManager = LocationServiceHelper()
    private let locationManager = CLLocationManager()
    var currentLocation:CLLocation?
    weak var delegate :LocationUpdateProtocol?
    private override init() {
        super.init()
        self.locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.distanceFilter = kCLLocationAccuracyHundredMeters
        locationManager.requestAlwaysAuthorization()
        locationManager.startUpdatingLocation()
    }

    // MARK: CLLocationManagerDelegate

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let delegate = self.delegate else {
            return
        }
        currentLocation = locations.first
        let userInfo:NSDictionary = ["location":currentLocation!]
        delegate.locationDidUpdateToLocation(location: currentLocation!)
        NotificationCenter.default.post(name: NSNotification.Name(rawValue: kLocationDidChangeNotification), object: self, userInfo: userInfo as? [AnyHashable : Any])
    }
}

我在下面的另一个class中调用了代表：

var locationServiceReference = LocationServiceHelper.sharedManager
    override func viewDidLoad() {
        super.viewDidLoad()
        fillFields()
      locationServiceReference.delegate = self
        self.mapView.showsUserLocation = true
    }

func locationDidUpdateToLocation(location: CLLocation) {
       // print(location)
        // let myLocation = CLLocationCoordinate2D(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)
        let myLocationForTesting = CLLocationCoordinate2D(latitude: 33.410165, longitude: 35.480060)
        myLocation = location
            let region = MKCoordinateRegion(center: myLocationForTesting, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))
        self.mapView.setRegion(region, animated: true)

    }

在 did update location 中，委托返回 nil，知道发生了什么吗？该函数未被调用，因为委托返回 nil。

Answer 1

确保您的控制器仍在内存中
你不需要使用守卫。可选链接在这种情况下效果更好：

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    currentLocation = locations.first
    let userInfo:NSDictionary = ["location":currentLocation!]
    delegate?.locationDidUpdateToLocation(location: currentLocation!)
    NotificationCenter.default.post(name: NSNotification.Name(rawValue: kLocationDidChangeNotification), object: self, userInfo: userInfo as? [AnyHashable : Any])
}

确保 func locationManager(_:didUpdateLocations) 在委托设置后调用。
对于未来，当委托更改为时，您希望传递最后一个位置：

weak var delegate :LocationUpdateProtocol? {
    didSet { 
        guard let last = currentLocation else { return }
        delegate?.locationDidUpdateToLocation(location: last)
    }
}

因为它是只有 1 个委托的单例，请确保您没有将委托设置为 nil 或其他地方的另一个短寿命对象

Answer 2

这段代码-

var locationServiceReference = LocationServiceHelper.sharedManager

在你的 delegate 设置之前执行，这就是为什么 delegate return nil 总是。

替换

var locationServiceReference = LocationServiceHelper.sharedManager

与

var locationServiceReference : LocationServiceHelper!

并在 viewDidLoad() 被调用后初始化。

override func viewDidLoad() {
    super.viewDidLoad()

    locationServiceReference = LocationServiceHelper.sharedManager
    locationServiceReference.delegate = self

}

希望对您有所帮助。如果您还有任何问题，请告诉我。

在 class 中调用后委托 return nil

delegate return nil after calling it in a class

delegates

swift

location-services