Question

我正在尝试在地图视图中显示用户当前位置，但我在位置管理器功能的第一行显示错误

这是我的代码

import UIKit
import MapKit

class FirstViewController: UIViewController, CLLocationManagerDelegate {

@IBOutlet weak var mapkitView: MKMapView!
var locationManager: CLLocationManager!

override func viewDidLoad()
{
    super.viewDidLoad()

    if (CLLocationManager.locationServicesEnabled())
    {
        locationManager = CLLocationManager()
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.requestAlwaysAuthorization()
        locationManager.startUpdatingLocation()
    }
}

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
{
    let location = locations.last as! CLLocation

    let center = CLLocationCoordinate2DMake(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)

    let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))

    self.mapkitView.setRegion(region, animated: true)
}
}

我得到的错误是“来自'CLLocation的'Downcast？' 'CLLocation'只能打开选项;你的意思是使用'！'？

在线让location = locations.last为！ CLLocation

Answer 1

你强迫Optional CLLocation加注CLLocation，这就是为什么斯威夫特建议只是强行打开它：

let location = locations.last!

如果locations为空，则此版本（和您的版本）将崩溃。

因此，我建议永远不要强制打开任何内容，而是使用guard代替：

guard let location = locations.last else {
    return
}

来自'CLLocation'的沮丧？ 'CLLocation'只展开选项;你的意思是用'！'？

1 个答案: