我正在绘制一条连接起点、途经点和终点的线，并将它们放入一个数组中并计算路径。一开始画得很好，但如果我第二次调用相同的方法，就会出现下面的错误，这在选择城市之间的长路线时发生，但如果我在城市内多次调用它（短路线），它就可以正常工作。
所以请问为什么我在长路上会出现错误？我的问题在哪里？
所以请问为什么我在长路上会出现错误？我的问题在哪里？
'Error Domain=MKErrorDomain Code=3 "Directions Not Available" UserInfo={NSLocalizedFailureReason=Route information is not available at this moment., MKErrorGEOError=-4, MKDirectionsErrorCode=2, NSLocalizedDescription=Directions Not Available'
func calculateRoute(wayPoint: [MKMapItem]) {
let request:MKDirectionsRequest = MKDirectionsRequest()
var allPointsArray: [MKMapItem] = []
var directions: MKDirections = MKDirections(request: request)
var directionsResponse: MKDirectionsResponse = MKDirectionsResponse()
var route: MKRoute = MKRoute()
for points in wayPoint{
allPointsArray.append(points)
}
for var i = 0; i < allPointsArray.count - 1; ++i {
request.source = allPointsArray[i]
request.destination = allPointsArray[i+1]
request.transportType = MKDirectionsTransportType.Automobile
request.requestsAlternateRoutes = false
directions = MKDirections(request: request)
directions.calculateDirectionsWithCompletionHandler { (response: MKDirectionsResponse?, error: NSError?) -> Void in
if error == nil {
directionsResponse = response!
route = directionsResponse.routes[0]
self.mapView.addOverlay(route.polyline, level: MKOverlayLevel.AboveRoads)
}else {
print(error)
}
}
}
}