Display multiple shapes on a map

import Mapbox
 
class ViewController: UIViewController, MGLMapViewDelegate {
 
var mapView: MGLMapView!
 
override func viewDidLoad() {
super.viewDidLoad()
 
// Configure a map view centered on Washington, D.C. 
mapView = MGLMapView(frame: view.bounds)
mapView.styleURL = MGLStyle.lightStyleURL
mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
mapView.setCenter(CLLocationCoordinate2D(latitude: 38.897435, longitude: -77.039679), zoomLevel: 12, animated: false)
mapView.delegate = self
 
view.addSubview(mapView)
}
 
func mapView(_ mapView: MGLMapView, didFinishLoading style: MGLStyle) {
 
// Since we know this file exists within this project, we'll force unwrap its value.
// If this data was coming from an external server, we would want to perform
// proper error handling for a web request/response.
let url = URL(fileURLWithPath: Bundle.main.path(forResource: "dc-metro", ofType: "geojson")!)
 
// Create a shape source and register it with the map style.
let source = MGLShapeSource(identifier: "transit", url: url, options: nil)
style.addSource(source)
 
// Add different line, point, and polygon shapes to the map style.
style.addLines(from: source)
style.addPoints(from: source)
style.addPolygons(from: source)
}
}
 
extension MGLStyle {
func addLines(from source: MGLShapeSource) {
/**
Configure a line style layer to represent a rail line, filtering out all data from the
source that is not of `Rail line` type. The `TYPE` is an attribute of the source data
that can be seen by inspecting the GeoJSON source file, for example:
 
{
"type": "Feature",
"properties": {
"NAME": "Dupont Circle",
"TYPE": "metro-station"
},
"geometry": {
"type": "Point",
"coordinates": [
-77.043416,
38.909605
]
},
"id": "994446c244acadeb15d3f9fc18278c73"
}
*/
let lineLayer = MGLLineStyleLayer(identifier: "rail-line", source: source)
lineLayer.predicate = NSPredicate(format: "TYPE = 'Rail line'")
lineLayer.lineColor = NSExpression(forConstantValue: UIColor.red)
lineLayer.lineWidth = NSExpression(forConstantValue: 2)
 
self.addLayer(lineLayer)
}
 
func addPoints(from source: MGLShapeSource) {
// Configure a circle style layer to represent rail stations, filtering out all data from
// the source that is not of `metro-station` type.
let circleLayer = MGLCircleStyleLayer(identifier: "stations", source: source)
circleLayer.predicate = NSPredicate(format: "TYPE = 'metro-station'")
circleLayer.circleColor = NSExpression(forConstantValue: UIColor.red)
circleLayer.circleRadius = NSExpression(forConstantValue: 6)
circleLayer.circleStrokeWidth = NSExpression(forConstantValue: 2)
circleLayer.circleStrokeColor = NSExpression(forConstantValue: UIColor.black)
 
self.addLayer(circleLayer)
}
 
func addPolygons(from source: MGLShapeSource) {
// Configure a fill style layer to represent polygon regions in Washington, D.C.
// Source data that is not of `neighborhood-region` type will be excluded.
let polygonLayer = MGLFillStyleLayer(identifier: "DC-regions", source: source)
polygonLayer.predicate = NSPredicate(format: "TYPE = 'neighborhood-region'")
polygonLayer.fillColor = NSExpression(forConstantValue: UIColor(red: 0.27, green: 0.41, blue: 0.97, alpha: 0.3))
polygonLayer.fillOutlineColor = NSExpression(forConstantValue: UIColor(red: 0.27, green: 0.41, blue: 0.97, alpha: 1.0))
 
self.addLayer(polygonLayer)
}
}