我是请求路线的新手，并关注 hackingwithswift 的文章（https://www.hackingwithswift.com/example-code/location/how-to-find-directions-using-mkmapview-and-mkdirectionsrequest）我能够在跟踪新路线时，获取我刚刚跟踪的路线的替代路线。我的目标是输入一个[CLLocation]get a route from MKDirection。问题是，在跟踪它时，我确实得到了一条替代路线，但是当从保存的路线（我刚刚跟踪的相同）请求它时，我得到一个response带有错误消息的 nil ：
方向错误：错误域=MKErrorDomain Code=1 "Indicazioni stradali non disponibili" UserInfo={NSLocalizedFailureReason=Le informazioni sull'itinerario non sono attualmente disponibili., MKErrorGEOError=-12, MKErrorGEOErrorUserInfo={ NSDebugDescription = "mapItem cannot be nil"; }, MKDirectionsErrorCode=3, NSLocalizedDescription=Indicazioni stradali non disponibili}
路线是一样的，所以起点和终点都是一样的。你能看到我在这里做错了什么吗？一如既往，非常感谢。
func repositionLocation(route: [CLLocation]) -> [CLLocation] {
var repositioned: [CLLocation] = []
let request = MKDirections.Request()
request.requestsAlternateRoutes = false
request.transportType = .walking
let directions = MKDirections(request: request)
let a = route.first?.coordinate
let b = route.last?.coordinate
print("a is: \(String(describing: a)), b is \(String(describing: b))") // prints correct CLLocationCoordinate2D
request.source = MKMapItem(placemark: MKPlacemark(coordinate: a!))
request.destination = MKMapItem(placemark: MKPlacemark(coordinate: b!))
directions.calculate { [unowned self] response, error in
if let err = error {
print("direction error : \(err)")
}
guard let unwrappedResponse = response else {print("no suggested routes available"); return } // here always returns
guard let coord = unwrappedResponse.routes.first?.steps else {return}
for location in coord {
let point: CLLocation = CLLocation(latitude: location.polyline.coordinate.latitude, longitude: location.polyline.coordinate.longitude)
repositioned.append(point)
}
}
return repositioned
}
更新 ：
我正在缩小问题的范围，因为我发出了太多请求（但我只发出了一个）并且服务器停止响应，或者由于响应异步，函数在它实际上可以得到有效响应之前退出，因为我是从 TableView 调用它。我将如何等待响应cellForRow？
更新 2：
经过宝贵的建议，它现在正在请求路线并获得响应，我从中CLLocation为每个步骤创建一个新的，并将其附加到repositioned完成时返回的数组中。实际上，当我打印它时，我实际上看到 newCLLocation在循环内正确创建for，但是数组的大小不会增加，并且返回的数组只会有来自输入路由的第一个追加。
该函数的较新版本是：
func repositionLocation(route: [CLLocation], completion: @escaping ([CLLocation]) -> Void) {
var pos = 0
var repositioned = [CLLocation]()
repositioned.append(route.first!)
guard route.count > 4 else {print("Reposision Location failed, not enough positions");return}
let request = MKDirections.Request()
request.requestsAlternateRoutes = false
request.transportType = .walking
while pos < route.count - 4 {
let a = repositioned.last!.coordinate
let b = route[pos + 4].coordinate
request.source = MKMapItem(placemark: MKPlacemark(coordinate: a))
request.destination = MKMapItem(placemark: MKPlacemark(coordinate: b))
let directions = MKDirections(request: request)
directions.calculate { [unowned self] response, error in
if let err = error {
print("direction error : \(err)")
}
guard let unwrappedResponse = response else {print("no suggested routes available"); return }
print("Response is: \(unwrappedResponse.debugDescription)")
guard let coord = unwrappedResponse.routes.first?.steps else {print("No coordinates");return}
print("coord is: \(coord)")
for location in coord {
let point: CLLocation = CLLocation(latitude: location.polyline.coordinate.latitude, longitude: location.polyline.coordinate.longitude)
print("point is: \(point)") // prints a correct CLLocation with coordinates
repositioned.append(point)
print("repositioned in for loop is : \(repositioned)") // prints just first appended location CLLocation with coordinates
}
}
print("repositioned in while loop is : \(repositioned)")
pos += 5
}
// last segment.
// let a = repositioned.last?.coordinate
// let b = route.last?.coordinate
//
// request.source = MKMapItem(placemark: MKPlacemark(coordinate: a!))
// request.destination = MKMapItem(placemark: MKPlacemark(coordinate: b!))
//
// let directions = MKDirections(request: request)
//
// directions.calculate { [unowned self] response, error in
// if let err = error {
// print("direction error : \(err)")
// }
// guard let unwrappedResponse = response else {print("no suggested routes available"); return }
// print("Response is: \(unwrappedResponse.debugDescription)")
// guard let coord = unwrappedResponse.routes.first?.steps else {print("No coordinates");return}
// for location in coord {
// let point: CLLocation = CLLocation(latitude: location.polyline.coordinate.latitude, longitude: location.polyline.coordinate.longitude)
// repositioned.append(point)
// }
print("repositioned at completion is : \(repositioned)")
completion(repositioned)
// }
}
不要看注释掉的部分，这将处理输入路由的最后一位，超出了内部while循环处理的部分。