谷歌地图导航（斯威夫特）

Question

我是初学者，我创建了这个VC

import UIKit
import CoreLocation
import GoogleMaps
import GooglePlaces

class FinalClass: UIViewController {

    @IBOutlet weak var containerView: UIView!
    @IBOutlet weak var bottomInfoView: UIView!
    @IBOutlet weak var descriptionLabel: UILabel!
    @IBOutlet weak var distanceLabel: UILabel!


    var userLocation:CLLocationCoordinate2D?
    var places:[QPlace] = []
    var index:Int = -1

    var mapView:GMSMapView!
    var marker:GMSMarker?

    override func loadView() {
        super.loadView()
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        guard index >= 0, places.count > 0 else {
            return

        }

        let place = places[index]
        let lat = place.location?.latitude ?? 1.310844
        let lng = place.location?.longitude ?? 103.866048

        // Google map view
        let camera = GMSCameraPosition.camera(withLatitude: lat, longitude: lng, zoom: 12.5)
        mapView = GMSMapView.map(withFrame: self.view.bounds, camera: camera)
        mapView.autoresizingMask = [.flexibleHeight, .flexibleWidth, .flexibleTopMargin, .flexibleBottomMargin, .flexibleLeftMargin, .flexibleRightMargin]
        self.containerView.addSubview(mapView)

        // Add gesture
        addSwipeGesture()

        didSelect(place: place)
        if userLocation != nil {
            addMarkerAtCurrentLocation(userLocation!)
        }
    }

    func addSwipeGesture() {
        let directions: [UISwipeGestureRecognizerDirection] = [.right, .left]
        for direction in directions {
            let gesture = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipe(sender:)))
            gesture.direction = direction
            self.bottomInfoView.addGestureRecognizer(gesture)
        }
    }

    func addMarkerAtCurrentLocation(_ userLocation: CLLocationCoordinate2D)  {
        let marker = GMSMarker()
        marker.position = userLocation
        marker.title = "Your location"
        marker.map = mapView
    }

    func didSelect(place:QPlace) {

        guard let coordinates = place.location else {
            return
        }

        // clear current marker
        marker?.map = nil

        // add marker
        marker = GMSMarker()
        marker?.position = coordinates
        marker?.title = place.name
        marker?.map = mapView
        mapView.selectedMarker = marker
        moveToMarker(marker!)

        // update bottom info panel view
        let desc = place.getDescription()
        descriptionLabel.text = desc.characters.count > 0 ? desc : "-"
        distanceLabel.text = "-"

        // update distance
        if userLocation != nil {
            let dist = distance(from: userLocation!, to: coordinates)
            distanceLabel.text = String.init(format: "Distance %.2f meters", dist)
        }

        title = place.name
    }

    func moveToMarker(_ marker: GMSMarker) {
        let camera = GMSCameraPosition.camera(withLatitude: marker.position.latitude,
                                              longitude: marker.position.longitude,
                                              zoom: 12.5)
        self.mapView.animate(to: camera)
    }

    // distance between two coordinates
    func distance(from: CLLocationCoordinate2D, to: CLLocationCoordinate2D) -> CLLocationDistance {
        let from = CLLocation(latitude: from.latitude, longitude: from.longitude)
        let to = CLLocation(latitude: to.latitude, longitude: to.longitude)
        return from.distance(from: to)
    }

    func handleSwipe(sender: UISwipeGestureRecognizer) {

        guard index >= 0, places.count > 0 else {
            return
        }

        if sender.direction == .left {
            if index < places.count - 2 {
                index += 1
                didSelect(place: places[index])
            }
        } else if sender.direction == .right {
            if index > 1 {
                index -= 1
                didSelect(place: places[index])
            }
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func lastBack(_ sender: Any) {

        dismiss(animated: true, completion: nil)

    }
}

其中（在前一个VC的用户定位的帮助下）显示了带有两个标记的goole地图，一个在用户位置，另一个在前一个VC中搜索的地点的位置（还有一些信息，如距离ecc。）我想要做的是在两点之间添加导航，所以我希望在视图加载时，自动导航开始。问题是我真的不知道如何实现这个功能，我找了一些教程，但没有人适合我的代码。 这是前一个VC中用于查找用户位置的代码

extension NearbyPlacesViewController: CLLocationManagerDelegate {

    func determineMyCurrentLocation() {
        locationManager = CLLocationManager()
        locationManager?.delegate = self
        locationManager?.desiredAccuracy = kCLLocationAccuracyBest
        locationManager?.requestWhenInUseAuthorization()
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        let userLocation:CLLocation = locations[0] as CLLocation

        manager.stopUpdatingLocation()

        print("user latitude = \(userLocation.coordinate.latitude)")
        print("user longitude = \(userLocation.coordinate.longitude)")

        didReceiveUserLocation(userLocation)
    }

    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        print("Error \(error)")
        errorGettingCurrentLocation(error.localizedDescription)
    }

    public func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        if status == .authorizedWhenInUse || status == .authorizedAlways {
            locationManager?.startUpdatingLocation()
            //locationManager.startUpdatingHeading()
        } else if status == .denied || status == .restricted {
            errorGettingCurrentLocation("Location access denied")
        }
    }

    func errorGettingCurrentLocation(_ errorMessage:String) {
        let alert = UIAlertController.init(title: "Error", message: errorMessage, preferredStyle: .alert)
        alert.addAction(UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil))
        present(alert, animated: true, completion: nil)
    }
}

因此，导航的起点是用户位置，结尾由let coordinates = place.location

表示