Add ios clustering example (#3608)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Bart Louwers <bart@emeel.net>

platform/ios/app-swift/Sources/ClusteringExample.swift

@@ -0,0 +1,71 @@
+import MapLibre
+import SwiftUI
+import UIKit
+
+class ClusteringExampleUIKit: UIViewController, MLNMapViewDelegate {
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        let mapView = MLNMapView(frame: view.bounds)
+        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+        mapView.delegate = self
+
+        mapView.setCenter(CLLocationCoordinate2D(latitude: 41.8864, longitude: -87.7135), zoomLevel: 2, animated: false)
+        view.addSubview(mapView)
+    }
+
+    func mapView(_: MLNMapView, didFinishLoading style: MLNStyle) {
+        guard let earthquakesJson = Bundle.main.url(forResource: "earthquakes", withExtension: "geojson"),
+              let data = try? Data(contentsOf: earthquakesJson),
+              let shape = try? MLNShape(data: data, encoding: String.Encoding.utf8.rawValue)
+        else {
+            preconditionFailure("Failed to load local GeoJSON file earthquakes.json")
+        }
+
+        let shapeSource = MLNShapeSource(
+            identifier: "earthquakes",
+            shape: shape,
+            options: [
+                .clustered: true,
+                .clusterRadius: 50,
+                .clusterMinPoints: 10,
+                .maximumZoomLevelForClustering: 14,
+            ]
+        )
+
+        style.addSource(shapeSource)
+
+        if let image = UIImage(named: "house-icon") {
+            style.setImage(image, forName: "home-symbol")
+        }
+
+        let unclusteredLayer = MLNSymbolStyleLayer(identifier: "unclustered-symbols", source: shapeSource)
+        unclusteredLayer.iconImageName = NSExpression(forConstantValue: "home-symbol")
+        unclusteredLayer.iconScale = NSExpression(forConstantValue: 0.5)
+        unclusteredLayer.predicate = NSPredicate(format: "cluster != YES")
+        style.addLayer(unclusteredLayer)
+
+        let clusterLayer = MLNCircleStyleLayer(identifier: "cluster-circles", source: shapeSource)
+        clusterLayer.circleColor = NSExpression(forConstantValue: UIColor.red)
+        clusterLayer.circleRadius = NSExpression(forConstantValue: 20)
+        clusterLayer.predicate = NSPredicate(format: "cluster == YES")
+        style.addLayer(clusterLayer)
+
+        let clusterCountLayer = MLNSymbolStyleLayer(identifier: "cluster-counts", source: shapeSource)
+        clusterCountLayer.text = NSExpression(format: "CAST(point_count, 'NSString')")
+        clusterCountLayer.textColor = NSExpression(forConstantValue: UIColor.white)
+        clusterCountLayer.textFontSize = NSExpression(forConstantValue: 12)
+        clusterCountLayer.predicate = NSPredicate(format: "cluster == YES")
+        style.addLayer(clusterCountLayer)
+    }
+}
+
+struct ClusteringExampleUIViewControllerRepresentable: UIViewControllerRepresentable {
+    typealias UIViewControllerType = ClusteringExampleUIKit
+
+    func makeUIViewController(context _: Context) -> ClusteringExampleUIKit {
+        ClusteringExampleUIKit()
+    }
+
+    func updateUIViewController(_: ClusteringExampleUIKit, context _: Context) {}
+}

platform/ios/app-swift/Sources/MapLibreNavigationView.swift

@@ -34,6 +34,9 @@ struct MapLibreNavigationView: View {
                 NavigationLink("AddMarkerExample") {
                     AddMarkerSymbolExampleUIViewControllerRepresentable()
                 }
+                NavigationLink("ClusteringExample") {
+                    ClusteringExampleUIViewControllerRepresentable()
+                }
                 NavigationLink("ObserverExample") {
                     ObserverExampleViewUIViewControllerRepresentable()
                 }