在 Swift 中计算预计到达时间

我试图快速计算两个位置之间的估计旅行时间（步行），用户进行注释。

这是我当前的代码，它不会引发任何导致程序崩溃的错误，而只会返回“请求 ETA 时出错”

import UIKit
import MapKit

class LocationObjects: NSObject, MKAnnotation {

/*let userView = CLLocation(latitude: mapView.centerCoordinate.latitude, longitude: mapView.centerCoordinate.longitude)
 let annotationPoint = CLLocation(latitude: annotation.coordinate.latitude, longitude: annotation.coordinate.longitude)
 let distance = userView.distance(from: annotationPoint)*/


var identifier = "bathroom location"
var title: String?
var coordinate: CLLocationCoordinate2D
var distance: Double
var phoneNumber: String
var addressFinished: String
var estimatedTravelTime: String


// Request ETA function
// Uses user location and destination to send request
// For Estimated time of arrival
class func requestETA(userCLLocation: CLLocation, coordinate: CLLocationCoordinate2D) -> String {

    var travelTime = String()

    let request = MKDirectionsRequest()
    /* Source MKMapItem */
    let sourceItem = MKMapItem(placemark: MKPlacemark(coordinate: userCLLocation.coordinate, addressDictionary: nil))
    request.source = sourceItem
    /* Destination MKMapItem */
    let destinationItem = MKMapItem(placemark: MKPlacemark(coordinate: coordinate, addressDictionary: nil))
    request.destination = destinationItem
    request.requestsAlternateRoutes = false
    // Looking for walking directions
    request.transportType = MKDirectionsTransportType.walking

    // You use the MKDirectionsRequest object constructed above to initialise an MKDirections object
    let directions = MKDirections(request: request)
    directions.calculateETA { (etaResponse, error) -> Void in
        if let error = error {
            print("Error while requesting ETA : \(error.localizedDescription)")
            travelTime = "Not Available"
        }else{
            print("No error requesting ETA")
            travelTime = "\(Int((etaResponse?.expectedTravelTime)!/60)) min"
        }
    }

    return travelTime
}


init(name:String,lat:CLLocationDegrees,long:CLLocationDegrees,userCLLocation:CLLocation, phone:String, address:String){
    title = name
    coordinate = CLLocationCoordinate2DMake(lat, long)
    distance = Double(String(format: "%.2f", (userCLLocation.distance(from: CLLocation(latitude: lat, longitude: long)))*0.000621371))!
    phoneNumber = phone
    addressFinished = address
    estimatedTravelTime = LocationObjects.requestETA(userCLLocation: userCLLocation, coordinate: coordinate)

}
}

对于非常长的行，控制台看起来像这样

    2017-05-26 13:53:51.583 Toilet Locator[2568:181698] didFailWithError Error Domain=GEOErrorDomain Code=-3 "(null)" UserInfo={GEORequestThrottleStateLevel=0, GEORequestThrottleStateResetTimeRemaining=34.019131004810333}
2017-05-26 13:53:51.584 Toilet Locator[2568:181698] didFailWithError Error Domain=GEOErrorDomain Code=-3 "(null)" UserInfo={GEORequestThrottleStateLevel=0, GEORequestThrottleStateResetTimeRemaining=34.018206000328064}
Error while requesting ETA : Directions Not Available
Error while requesting ETA : Directions Not Available

希望大家给予指导，谢谢大家！

注意：ViewController 连续多次调用此类，因此不确定这是否会导致 Apple 拒绝 ETA 请求？