Create a heatmap layer | Maps SDK v6 | iOS

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ViewController
github View on GitHub
Swift
Objective-C
import Mapbox

class HeatmapExample: UIViewController, MGLMapViewDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Create and add a map view.
        let mapView = MGLMapView(frame: view.bounds, styleURL: MGLStyle.lightStyleURL)
        mapView.autoresizingMask = [.flexibleHeight, .flexibleWidth]
        mapView.delegate = self
        mapView.tintColor = .lightGray
        view.addSubview(mapView)
    }

    func mapView(_ mapView: MGLMapView, didFinishLoading style: MGLStyle) {
        // Parse GeoJSON data. This example uses all M1.0+ earthquakes from 12/22/15 to 1/21/16 as logged by USGS' Earthquake hazards program.
        guard let url = URL(string: "https://www.mapbox.com/mapbox-gl-js/assets/earthquakes.geojson") else { return }
        let source = MGLShapeSource(identifier: "earthquakes", url: url, options: nil)
        style.addSource(source)

        // Create a heatmap layer.
        let heatmapLayer = MGLHeatmapStyleLayer(identifier: "earthquakes", source: source)

        // Adjust the color of the heatmap based on the point density.
        let colorDictionary: [NSNumber: UIColor] = [
                                0.0: .clear,
                               0.01: .white,
                               0.15: UIColor(red: 0.19, green: 0.30, blue: 0.80, alpha: 1.0),
                                0.5: UIColor(red: 0.73, green: 0.23, blue: 0.25, alpha: 1.0),
                                  1: .yellow
        ]
        heatmapLayer.heatmapColor = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($heatmapDensity, 'linear', nil, %@)", colorDictionary)

        // Heatmap weight measures how much a single data point impacts the layer's appearance.
        heatmapLayer.heatmapWeight = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(mag, 'linear', nil, %@)",
                                                  [0: 0,
                                                   6: 1])

        // Heatmap intensity multiplies the heatmap weight based on zoom level.
        heatmapLayer.heatmapIntensity = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                                              [0: 1,
                                               9: 3])
        heatmapLayer.heatmapRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                                           [0: 4,
                                            9: 30])

        // The heatmap layer should be visible up to zoom level 9.
        heatmapLayer.heatmapOpacity = NSExpression(format: "mgl_step:from:stops:($zoomLevel, 0.75, %@)", [0: 0.75, 9: 0])
        style.addLayer(heatmapLayer)

        // Add a circle layer to represent the earthquakes at higher zoom levels.
        let circleLayer = MGLCircleStyleLayer(identifier: "circle-layer", source: source)

        let magnitudeDictionary: [NSNumber: UIColor] = [
                                                        0: .white,
                                                      0.5: .yellow,
                                                      2.5: UIColor(red: 0.73, green: 0.23, blue: 0.25, alpha: 1.0),
                                                        5: UIColor(red: 0.19, green: 0.30, blue: 0.80, alpha: 1.0)
        ]
        circleLayer.circleColor = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(mag, 'linear', nil, %@)", magnitudeDictionary)

        // The heatmap layer will have an opacity of 0.75 up to zoom level 9, when the opacity becomes 0.
        circleLayer.circleOpacity = NSExpression(format: "mgl_step:from:stops:($zoomLevel, 0, %@)", [0: 0, 9: 0.75])
        circleLayer.circleRadius = NSExpression(forConstantValue: 20)
        style.addLayer(circleLayer)
    }
}