Swift如何从我在搜索栏中定义的地图项目构建路径

import MapKit

let mapView = MKMapView()

let region = MKCoordinateRegion(center: CLLocationCoordinate2D(latitude: 37.7749, longitude: -122.4194), span: MKCoordinateSpan(latitudeDelta: 0.1, longitudeDelta: 0.1))
mapView.setRegion(region, animated: true)

let sourcePlacemark = MKPlacemark(coordinate: CLLocationCoordinate2D(latitude: 37.7749, longitude: -122.4194))
let destinationPlacemark = MKPlacemark(coordinate: CLLocationCoordinate2D(latitude: 37.3352, longitude: -122.0096))

let sourceMapItem = MKMapItem(placemark: sourcePlacemark)
let destinationMapItem = MKMapItem(placemark: destinationPlacemark)
let directionRequest = MKDirections.Request()
directionRequest.source = sourceMapItem
directionRequest.destination = destinationMapItem
directionRequest.transportType = .automobile

let directions = MKDirections(request: directionRequest)
directions.calculate { (response, error) in
    guard let route = response?.routes.first else {
        // 处理错误情况
        return
    }
    // 在地图上绘制路径
    self.mapView.addOverlay(route.polyline)
}

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is MKPolyline {
        let renderer = MKPolylineRenderer(overlay: overlay)
        renderer.strokeColor = UIColor.blue
        renderer.lineWidth = 5
        return renderer
    }
    return MKOverlayRenderer()
}