我是请求路线的新手，并且遵循hackingwithswift(https://www.hackingwithswift.com/example-code/location/how-to-find-directions-using-mkmapview-and-mkdirectionsrequest(的文章，在跟踪新路线时，我能够获得我刚刚跟踪的路线的替代路线。我的目标是输入一个[CLLocation]从MKDirection获取路线。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请求它时(与我刚刚跟踪的路线相同(，我收到一条带有错误消息的零response：
方向错误：错误域=MKError域代码=1"Indicazioni stradali non disponibili" UserInfo={NSLocalizedFailureReason=Le informazioni sull'itinerario non sono attualmente disponibili.， MKErrorGEOError=-12， MKErrorGEOErrorUserInfo={ NSDebugDescription = "mapItem 不能为零";}， MKDirectionsErrorCode=3， NSLocalizedDescription=Indicazioni stradali non disponibili}
路线相同，因此起点和终点相同。你能看到我在这里做错了什么吗？ 一如既往地非常感谢。
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，要么我发出太多请求(但我只发出一个(并且服务器停止响应，要么作为异步响应，函数在实际获得有效响应之前退出，因为我从 TableView 调用它。 我将如何等待cellForRow的响应？
更新 2：
在宝贵的建议之后，它现在请求路由并获得响应，我从中为每个步骤创建一个新CLLocation，并将其附加到完成后返回的repositioned数组中。 我实际上看到在打印新CLLocation时在for循环中正确创建，但数组的大小不会增加，并且返回的数组将仅具有输入路由的第一个附加。
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，超过循环内处理的部分while。
有几个问题：
首先，您正在尝试建立一条穿越整个美国的步行路线-这个问题无法通过常规方法解决。我建议将点的坐标设置在更近的距离。我已经在更近的地方测试了您的代码，并且出现了路线。
其次，您可以使用以下代码：
func repositionLocation(route: [CLLocation], completion: @escaping ([CLLocation]) -> Void) {
var repositioned = [CLLocation]()
let request = MKDirections.Request()
request.requestsAlternateRoutes = false
request.transportType = .walking
let a = route.first?.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)
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 { 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
for route in unwrappedResponse.routes {
self.mapView.addOverlay(route.polyline)
self.mapView.setVisibleMapRect(route.polyline.boundingMapRect, animated: true)
}
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)
}
completion(repositioned)
}
}
您可以设置let directions = MKDirections(request: request)，但只有这样才能配置request.source和request.destination。除此之外，您可以异步获取结果，因此我为结果添加了completion。
对于测试，您可以调用：
repositionLocation(route: [CLLocation(latitude: 40.7127, longitude: -74.0059), CLLocation(latitude: 40.79, longitude: -74.011)]) { result in
print(result)
}
UPD2：
@Vincenzo如我所见，您错误地使用完成处理程序进行闭包，我建议您阅读有关异步和闭包的信息。
我建议使用以下代码：
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
}
completion(repositioned)
}
print("repositioned in while loop is : (repositioned)")
pos += 5
}
}