上下文閉包類型……期望 2 個 arguments，但閉包體中使用了 3 個

Question

親愛的高級程序員，

您能否協助一個相當新的程序員編輯此代碼。 似乎新版本的 Xcode 不支持以下代碼並顯示錯誤：

 **"Contextual closure type '(Directions.Session, Result<RouteResponse, DirectionsError>) -> Void' (aka '((options: DirectionsOptions, credentials: DirectionsCredentials), Result<RouteResponse, DirectionsError>) -> ()') expects 2 arguments, but 3 were used in closure body"** 

代碼直接從 mapbox 文檔網站復制而來。 任何形式的幫助將不勝感激。 提前致謝。

func getRoute(from origin: CLLocationCoordinate2D,
              to destination: MGLPointFeature) -> [CLLocationCoordinate2D]{
    
    var routeCoordinates : [CLLocationCoordinate2D] = []
    let originWaypoint = Waypoint(coordinate: origin)
    let destinationWaypoint = Waypoint(coordinate: destination.coordinate)
    
    let options = RouteOptions(waypoints: [originWaypoint, destinationWaypoint], profileIdentifier: .automobileAvoidingTraffic)
    
    _ = Directions.shared.calculate(options) { (waypoints, routes, error) in    
        
        guard error == nil else {
            print("Error calculating directions: \(error!)")
            return
        }
        
        guard let route = routes?.first else { return }
        routeCoordinates = route.coordinates!
        self.featuresWithRoute[self.getKeyForFeature(feature: destination)] = (destination, routeCoordinates)
    }
    return routeCoordinates
}

Answer 1

請開發人員學習閱讀錯誤消息和/或文檔。

錯誤清楚地表明閉包的類型是(Directions.Session, Result<RouteResponse, DirectionsError>) -> Void (2 個參數)，它代表一個 session (一個元組) 和一個包含響應和潛在錯誤的自定義Result類型.

你必須寫一些像

_ = Directions.shared.calculate(options) { (session, result) in 

    switch result {
       case .failure(let error): print(error)
       case .success(let response): 
          guard let route = response.routes?.first else { return }
          routeCoordinates = route.coordinates!
          self.featuresWithRoute[self.getKeyForFeature(feature: destination)] = (destination, routeCoordinates)
    }   
}

除了這個問題之外，不可能從異步任務中返回某些東西，例如，您必須添加一個完成處理程序

func getRoute(from origin: CLLocationCoordinate2D,
          to destination: MGLPointFeature, 
          completion: @escaping ([CLLocationCoordinate2D]) -> Void) {

並在閉包內的success案例結束時調用completion(route.coordinates!)