ios - How to streamline multiple coordinate poly line entries in MKMapKit

Question

I am trying to add multiple poly lines onto a map using mkmapkit. These poly lines indicate walking zones in my area. The problem is that my code is too bulky for a large amount of walking zones.

At the moment my code only indicates 2 walking routes but for instance if I want to add 100 or 1000 walking routes the code would be massive. I'm sure there is a way I could stream line this code so I could add in multiple walking zones with a lot less code but in not too sure the best way to go about it.

import UIKit
import MapKit

class customPin: NSObject, MKAnnotation {
var coordinate: CLLocationCoordinate2D
var title: String?
var subtitle: String?

init(pinTitle:String, pinSubTitle:String, location:CLLocationCoordinate2D) {
    self.title = pinTitle
    self.subtitle = pinSubTitle
    self.coordinate = location
}
}

class ViewController: UIViewController, MKMapViewDelegate {

@IBOutlet weak var mapView: MKMapView!
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    //co-ordinates
    let zone1S = CLLocationCoordinate2D(latitude: 52.100525, longitude: -9.623071)
    let zone1E = CLLocationCoordinate2D(latitude: 52.07241, longitude: -9.575299)

    let zone2S = CLLocationCoordinate2D(latitude: 52.054161, longitude: -9.385031)
    let zone2E = CLLocationCoordinate2D(latitude: 52.081185, longitude: -9.247033)


    //pins
    let zone1PinS = customPin(pinTitle: "Zone 1 Start", pinSubTitle: "", location: zone1S)
    let zone1PinE = customPin(pinTitle: "Zone 1 End", pinSubTitle: "", location: zone1E)
    self.mapView.addAnnotation(zone1PinS)
    self.mapView.addAnnotation(zone1PinE)

    let zone2PinS = customPin(pinTitle: "Zone 2 Start", pinSubTitle: "", location: zone2S)
    let zone2PinE = customPin(pinTitle: "Zone 2 End", pinSubTitle: "", location: zone2E)
    self.mapView.addAnnotation(zone2PinS)
    self.mapView.addAnnotation(zone2PinE)


    let zone1PlacemarkS = MKPlacemark(coordinate: zone1S)
    let zone1PlacemarkE = MKPlacemark(coordinate: zone1E)

    let zone2PlacemarkS = MKPlacemark(coordinate: zone2S)
    let zone2PlacemarkE = MKPlacemark(coordinate: zone2E)


    //add polyline to map
    let directionRequestZone1 = MKDirections.Request()
    directionRequestZone1.source = MKMapItem(placemark: zone1PlacemarkS)
    directionRequestZone1.destination = MKMapItem(placemark: zone1PlacemarkE)

    let directionRequestZone2 = MKDirections.Request()
    directionRequestZone2.source = MKMapItem(placemark: zone2PlacemarkS)
    directionRequestZone2.destination = MKMapItem(placemark: zone2PlacemarkE)


    //type of commute
    directionRequestZone1.transportType = .automobile
     directionRequestZone2.transportType = .automobile


    let directions1 = MKDirections(request: directionRequestZone1)
    directions1.calculate { (response, error) in
        guard let directionResonse = response else {
            if let error = error {
                print("we have error getting directions==(error.localizedDescription)")
            }
            return
        }

        let route = directionResonse.routes[0]
        self.mapView.addOverlay(route.polyline, level: .aboveRoads)


        let rect = route.polyline.boundingMapRect
        //zooming in on location
       // self.mapView.setRegion(MKCoordinateRegion(rect), animated: true)
    }


    let directions2 = MKDirections(request: directionRequestZone2)
    directions2.calculate { (response, error) in
        guard let directionResonse = response else {
            if let error = error {
                print("we have error getting directions==(error.localizedDescription)")
            }
            return
        }

        let route2 = directionResonse.routes[0]
        self.mapView.addOverlay(route2.polyline, level: .aboveRoads)


        let rect = route2.polyline.boundingMapRect
        //zooming in on location
       // self.mapView.setRegion(MKCoordinateRegion(rect), animated: true)
    }


    //set delegate for mapview
    self.mapView.delegate = self
}


func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    let renderer = MKPolylineRenderer(overlay: overlay)
    renderer.strokeColor = UIColor.red
    renderer.lineWidth = 5.0
    return renderer
}
}

This is how it looks:

UPDATE: My attempt to use loops hasn't worked. I seem to have a loop working for dropping the start and end zone pins however it doesn't seem to work for drawing the poly lines.

        struct Location {
        let title: String
        let latitude: Double
        let longitude: Double
    }

    let locationsStart = [
        Location(title: "Start",    latitude: 52.100525, longitude: -9.623071)
    ]

    let locationsEnd = [
        Location(title: "End",    latitude: 52.07241, longitude: -9.575299)
    ]

    for location in locationsStart {
        let annotation = MKPointAnnotation()
        annotation.title = location.title
        annotation.coordinate = CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude)
        mapView.addAnnotation(annotation)

        let directionRequestZone1 = MKDirections.Request()
        let zonePlacemarkS = MKPlacemark(coordinate: CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude))
        let directionRequest = MKDirections.Request()
        directionRequest.source = MKMapItem(placemark: zonePlacemarkS)
        directionRequestZone1.transportType = .automobile
    }

    for location in locationsEnd {
        let annotation = MKPointAnnotation()
        annotation.title = location.title
        annotation.coordinate = CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude)
        mapView.addAnnotation(annotation)

        let directionRequestZone1 = MKDirections.Request()
        let zonePlacemarkE = MKPlacemark(coordinate: CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude))
        let directionRequest = MKDirections.Request()
        directionRequest.destination = MKMapItem(placemark: zonePlacemarkE)
        directionRequestZone1.transportType = .automobile

        let directions1 = MKDirections(request: directionRequestZone1)
        directions1.calculate { (response, error) in
            guard let directionResonse = response else {
                if let error = error {
                    print("we have error getting directions==(error.localizedDescription)")
                }
                return
            }

            let route = directionResonse.routes[0]
            self.mapView.addOverlay(route.polyline, level: .aboveRoads)


            let rect = route.polyline.boundingMapRect
        }
    }
           //set delegate for mapview
           self.mapView.delegate = self
}


func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    let renderer = MKPolylineRenderer(overlay: overlay)
    renderer.strokeColor = UIColor.red
    renderer.lineWidth = 5.0
    return renderer
}

Answer 1

I adapted your code as follows:

let zone1S = CLLocationCoordinate2D(latitude: 52.100525, longitude: -9.623071)
let zone1E = CLLocationCoordinate2D(latitude: 52.07241, longitude: -9.575299)
let zone2S = CLLocationCoordinate2D(latitude: 52.054161, longitude: -9.385031)
let zone2E = CLLocationCoordinate2D(latitude: 52.081185, longitude: -9.247033)

let zones = [(start:zone1S, end:zone1E), (start:zone2S, end:zone2E)]
for (i, zone) in zones.enumerated() {
    let pinS = customPin(pinTitle: "Zone (i+1) Start", pinSubTitle: "", location: zone.start)
    let pinE = customPin(pinTitle: "Zone (i+1) End", pinSubTitle: "", location: zone.end)
    self.mapView.addAnnotation(pinS)
    self.mapView.addAnnotation(pinE)
    let placeS = MKPlacemark(coordinate: zone.start)
    let placeE = MKPlacemark(coordinate: zone.end)
    let req = MKDirections.Request()
    req.source = MKMapItem(placemark: placeS)
    req.destination = MKMapItem(placemark: placeE)
    req.transportType = .automobile
    let dir = MKDirections(request: req)
    dir.calculate { (response, error) in
        guard let directionResponse = response else {
            if let error = error {
                print("we have error getting directions==(error.localizedDescription)")
            }
            return
        }
        DispatchQueue.main.async {
            let route = directionResponse.routes[0]
            self.mapView.addOverlay(route.polyline, level: .aboveRoads)
        }
    }
}

Clearly this can be trivially extended to any number of zones. (It may be that we should be using something like a DispatchGroup to prevent the networking calculate calls from piling up too quickly, but the goal was to solve it for two pairs of coordinates and this seems to work fine.)