无法从单独的变量/常量中的 CLLocationManager 获取坐标

Question

我试图在 Swift 中使用一个函数的值来设置一个变量/常量，该函数在应用程序打开时查找用户的当前位置。当我取消注释打印函数时，它成功打印了坐标，但我无法访问函数之外的值。

我目前将此作为我的代码的一部分，它在 MainVC.swift 文件中作为 MainVC 类的一部分：

import UIKit
import MapKit
import CoreLocation

class MainVC: UIViewController, CLLocationManagerDelegate {
    //Map
    @IBOutlet weak var map: MKMapView!

    let manager = CLLocationManager()
    let coordinates = locationManager()
    //I've also tried using let coordinates = currentCoords

    override func viewDidLoad() {
        super.viewDidLoad()

        manager.delegate = self
        manager.desiredAccuracy = kCLLocationAccuracyBest
        manager.requestWhenInUseAuthorization()
        manager.startUpdatingLocation()
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) -> String {
        let location = locations[0]

        let span:MKCoordinateSpan = MKCoordinateSpanMake(0.01, 0.01)
        let myLocation:CLLocationCoordinate2D = CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude)
        let region:MKCoordinateRegion = MKCoordinateRegionMake(myLocation, span)
        map.setRegion(region, animated: true)
        lat = String(myLocation.latitude)
        long = String(myLocation.longitude)
        let currentCoords:String = "\(lat);\(long)"

        //print(currentCoords)
        self.map.showsUserLocation = true

        return currentCoords
    }
}

但是我遇到了这个错误：

“不能在属性初始化器中使用实例成员 'locationManager'；属性初始化器在 'self' 可用之前运行”。

当我更改代码并使用时

let coordinates = currentCoords

我得到另一个错误显示：

“使用未解析的标识符‘currentCoords’”

我也尝试过使用lazy var 和lazy let。

Answer 1

这就是您定义公共变量的方式

let coordinates:CLLocation = nil

然后在您的 didUpdateLocations 中为坐标变量分配位置数组的最后一个元素。然后，您将可以在任何地方访问它。 请记住，didUpdateLocations 最多可能会在几秒钟后被调用，因此您的公共变量坐标将在最多几秒钟后被填充。

func coordinatesBecomeAvailable() {
    // Here you can print your coordinates or start using them for the first time
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
 let firstTime:Bool = (coordinates == nil)
 coordinates = locations[0]
 if (firstTime) // This is first time this function is called
     coordinatesBecomeAvailable()
 ......
 < Rest of your code here >
 ......
 < This function does have any return value! no String nothing >
 }

你只需要检查坐标的值是否为零。 或者您可以在 didUpdateLocations 内部检查这是否是第一次调用此委托方法。 这不是初始化和使用位置管理器的最有效和最完整的方法，我假设您刚刚发布了与您的问题相关的代码。

Answer 2

您应该能够像我的 buttonClick 方法一样访问 locationManager.location?.coordinate ：

import UIKit
import MapKit

class ViewController: UIViewController,CLLocationManagerDelegate,MKMapViewDelegate {

    let locationManager = CLLocationManager()

    @IBAction func buttonClick(_ sender: Any) {
        let location = locationManager.location?.coordinate
        let lat:Double = (location?.latitude)!
        let lon:Double = (location?.longitude)!
        print(lat,lon)
    }

    @IBOutlet weak var mapView: MKMapView!

        override func viewDidLoad() {
        super.viewDidLoad()

        mapView.delegate = self
        mapView.showsUserLocation = true
        mapView.userTrackingMode = .follow

        locationManager.delegate = self
        locationManager.distanceFilter = kCLLocationAccuracyNearestTenMeters
        locationManager.desiredAccuracy = kCLLocationAccuracyBest

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        print("viewDidAppear")
        // status is not determined
        if CLLocationManager.authorizationStatus() == .notDetermined {
            locationManager.requestAlwaysAuthorization()
        }
            // authorization were denied
        else if CLLocationManager.authorizationStatus() == .denied {
            showAlert("Location services were previously denied. Please enable location services for this app in Settings.")
        }
            // we do have authorization
        else if CLLocationManager.authorizationStatus() == .authorizedAlways {
            locationManager.startUpdatingLocation()
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        print("didUpdateLocations")
        print(locations.last?.coordinate)
    }

    func showAlert(_ title: String) {
        let alert = UIAlertController(title: title, message: nil, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
            alert.dismiss(animated: true, completion: nil)
        }))
        self.present(alert, animated: true, completion: nil)

    }
}