iOS Swift：Mapbox 路由计算不起作用，“类型'Result<RouteResponse, DirectionsError>' 的值没有成员'first'”

编程问答 2022-09-08

问题描述

因此，我正在学习我在 YT 上找到的教程“构建 iOS 应用程序：(2/4) 使用 MapBox 导航 SDK 计算路线”，但在尝试自行操作时遇到了问题。

不知何故，xCode 在创建 calculateRoute 函数时抛出了多个错误，尤其是在 Directions.shared.calculate(..) 中。这是我的代码：

import UIKit
import MapBox
import MapBoxNavigation
import MapBoxDirections
import MapboxcoreNavigation

class ThirdViewController: UIViewController,MGLMapViewDelegate{

//is the View that shows the map
var mapView: NavigationMapView!

//Saves the route
var directionsRoute: Route?

//creates the button
var navigateButton: UIButton!



override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    
    //view.backgroundColor = UIColor(red: 0.19,green: 0.21,blue: 0.24,alpha: 1.00)
    mapView = NavigationMapView(frame: view.bounds)
    mapView.autoresizingMask = [.flexibleWidth,.flexibleHeight]
    view.addSubview(mapView)
    
    mapView.delegate = self
    mapView.showsUserLocation = true
    mapView.setUserTrackingMode(.follow,animated: true)
    
    addButton()
    
}

func addButton(){
    navigateButton = UIButton(frame: CGRect(x: (view.frame.width/2) - 100,y: view.frame.height - 200,width: 200,height: 50))
    navigateButton.backgroundColor = UIColor.white
    navigateButton.setTitle("Route finden",for: .normal)
    navigateButton.setTitleColor(UIColor(red: 59/255,green: 178/255,blue: 208/255,alpha: 1),for: .normal)
    navigateButton.titleLabel?.font = UIFont(name: "AvenirNext-Demibold",size: 18)
    navigateButton.layer.cornerRadius = 25
    navigateButton.layer.shadowOffset = CGSize(width: 0,height: 10)
    //navigateButton.layer.shadowColor = C
    navigateButton.layer.shadowRadius = 5
    navigateButton.layer.shadowOpacity = 0.3
    navigateButton.addTarget(self,action: #selector(navigateButtonWaspressed(_:)),for: .touchUpInside)
    view.addSubview(navigateButton)
}

@objc func navigateButtonWaspressed(_ sender: UIButton){
    
}

func calculateRoute(from originCoor: CLLocationCoordinate2D,to destinationCoor: CLLocationCoordinate2D,completion: @escaping (Route?,Error?) -> Void ){
    let origin = Waypoint(coordinate: originCoor,coordinateAccuracy: -1,name: "Start")
    let destination = Waypoint(coordinate: destinationCoor,name: "Finish")
    
    let options = NavigationRouteOptions(waypoints: [origin,destination],profileIdentifier: .automobileAvoidingTraffic)
    
    _ = Directions.shared.calculate(options,completionHandler: { (wayponts,routes,error) in
        self.directionsRoute = routes?.first //HERE IS THE ERROR
        
        let coordinateBounds = MGLCoordinateBounds(sw: destinationCoor,ne: originCoor)
    })
}

}

我已经标记了导致问题的那一行。 xCode 告诉抛出以下错误：

  1. 上下文闭包类型'(Directions.Session,Result) -> Void' (又名'((options: DirectionsOptions,credentials: DirectionsCredentials),Result) -> ()')需要 2 个参数，但在闭包体中使用了 3 个 一旦我从上面的 lign 中删除第三个参数（错误），就会出现两个新错误： 2) 'Result' 类型的值没有成员 'first' 3) 不能对 'Result'
    2. 类型的非可选值使用可选链

我似乎无法修复它，因为我是初学者。我也找不到任何关于它的文档。 这行代码应该将 DirectionsRoute 设置为返回的路线中的第一条路线。我一步一步地跟着教程，我错过了什么吗？ 谢谢！

解决方法

第二个参数——只有两个——是一个 Result 类型，一个带有关联值的枚举。它包含 routes 和 error

你必须写

_ = Directions.shared.calculate(options,completionHandler: { (waypoints,result) in
    switch result {
        case .success(let response):
            guard let route = response.routes?.first else { return }
            self.directionsRoute = route
            let coordinateBounds = MGLCoordinateBounds(sw: destinationCoor,ne: originCoor)
        case .failure(let error): print(error)
    }  
})
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