SwiftUI - Clustering data
This example demonstrates how to create point clusters with the Mapbox Maps SDK for iOS. The ClusteringExample struct includes a map view with clustering functionality for fire hydrant data. The map displays clustered and unclustered points, and when tapped, shows details such as the hydrant asset number, location, cluster IDs, and point counts.
Clustering requires a GeoJSONSource with its cluster property set to true. Points that should be rendered as a cluster will contain additional properties used to style them differently.
Three layers are then added that use the clustered source, one for unclustered points, one for cluster points, and one for displaying the cluster count.
iOS Examples App Available
This example code is part of the Maps SDK for iOS Examples App, a working iOS project available on Github. iOS developers are encouraged to run the examples app locally to interact with this example in an emulator and explore other features of the Maps SDK.
See our Run the Maps SDK for iOS Examples App tutorial for step-by-step instructions.
ClusteringExample.swift
import SwiftUI
import MapboxMaps
private enum Id {
static let clusterCircle = "clustered-circle-layer"
static let point = "unclustered-point-layer"
static let count = "cluster-count-layer"
static let source = "fire-hydrant-source"
}
@available(iOS 14.0, *)
struct ClusteringExample: View {
struct Detail: Identifiable {
var id = UUID()
var title: String
var message: String
}
@State var details: Detail?
var body: some View {
MapReader { proxy in
Map(initialViewport: .camera(center: .dc, zoom: 10))
.mapStyle(.dark)
.onStyleLoaded { _ in
// This example uses direct style manipulation with MapboxMap
guard let map = proxy.map else { return }
try! setupClusteringLayer(map)
}
.onLayerTapGesture(Id.clusterCircle) { feature, _ in
details = Detail(queriedFeature: feature)
return true
}
.onLayerTapGesture(Id.point) { feature, _ in
details = Detail(queriedFeature: feature)
return true
}
.onMapTapGesture { context in
let latLon = String(format: "%.4f, %.4f", context.coordinate.latitude, context.coordinate.longitude)
details = Detail(title: "Map Tapped", message: "\(latLon)")
}
.ignoresSafeArea()
.alert(item: $details) {
Alert(title: Text($0.title), message: Text($0.message))
}
}
}
}
@available(iOS 14.0, *)
extension ClusteringExample.Detail {
init(title: String, message: String) {
self.title = title
self.message = message
}
init?(queriedFeature: QueriedFeature) {
guard let properties = queriedFeature.feature.properties else {
return nil
}
if case let .string(assetnum) = properties["ASSETNUM"],
case let .string(loc) = properties["LOCATIONDETAIL"] {
title = "Hydrant \(assetnum)"
message = "\(loc)"
} else if case let .number(pointCount) = properties["point_count"],
case let .number(clusterId) = properties["cluster_id"] {
title = "Cluster ID \(Int(clusterId))"
message = "There are \(Int(pointCount)) points in this cluster"
} else {
return nil
}
}
}
@available(iOS 14.0, *)
private func setupClusteringLayer(_ map: MapboxMap) throws {
// The image named `fire-station-11` is included in the app's Assets.xcassets bundle.
// In order to recolor an image, you need to add a template image to the map's style.
// The image's rendering mode can be set programmatically or in the asset catalogue.
let image = UIImage(named: "fire-station-11")!.withRenderingMode(.alwaysTemplate)
// Add the image to the map's style. Set `sdf` to `true`. This allows the icon images to be recolored.
// For more information about `SDF`, or Signed Distance Fields, see
// https://docs.mapbox.com/help/troubleshooting/using-recolorable-images-in-mapbox-maps/#what-are-signed-distance-fields-sdf
try! map.addImage(image, id: "fire-station-icon", sdf: true)
// Fire_Hydrants.geojson contains information about fire hydrants in the District of Columbia.
// It was downloaded on 6/10/21 from https://opendata.dc.gov/datasets/DCGIS::fire-hydrants/about
let url = Bundle.main.url(forResource: "Fire_Hydrants", withExtension: "geojson")!
// Create a GeoJSONSource using the previously specified URL.
var source = GeoJSONSource(id: "fire-hydrant-source")
source.data = .url(url)
// Enable clustering for this source.
source.cluster = true
source.clusterRadius = 75
let clusteredLayer = createClusteredLayer()
let unclusteredLayer = createUnclusteredLayer()
// `clusterCountLayer` is a `SymbolLayer` that represents the point count within individual clusters.
let clusterCountLayer = createNumberLayer()
// Add the source and two layers to the map.
try map.addSource(source)
try map.addLayer(clusteredLayer)
try map.addLayer(unclusteredLayer, layerPosition: LayerPosition.below(clusteredLayer.id))
try map.addLayer(clusterCountLayer)
}
@available(iOS 14.0, *)
private func createClusteredLayer() -> CircleLayer {
// Create a symbol layer to represent the clustered points.
var clusteredLayer = CircleLayer(id: Id.clusterCircle, source: Id.source)
// Filter out unclustered features by checking for `point_count`. This
// is added to clusters when the cluster is created. If your source
// data includes a `point_count` property, consider checking
// for `cluster_id`.
clusteredLayer.filter = Exp(.has) { "point_count" }
// Set the color of the circles based on the number of points within
// a given cluster. The first value is a default value.
clusteredLayer.circleColor = .expression(Exp(.step) {
Exp(.get) { "point_count" }
UIColor.systemGreen
50
UIColor.systemBlue
100
UIColor.systemRed
})
clusteredLayer.circleRadius = .constant(25)
return clusteredLayer
}
@available(iOS 14.0, *)
private func createUnclusteredLayer() -> SymbolLayer {
// Create a symbol layer to represent the points that aren't clustered.
var unclusteredLayer = SymbolLayer(id: Id.point, source: Id.source)
// Filter out clusters by checking for `point_count`.
unclusteredLayer.filter = Exp(.not) {
Exp(.has) { "point_count" }
}
unclusteredLayer.iconImage = .constant(.name("fire-station-icon"))
unclusteredLayer.iconColor = .constant(StyleColor(.white))
// Rotate the icon image based on the recorded water flow.
// The `mod` operator allows you to use the remainder after dividing
// the specified values.
unclusteredLayer.iconRotate = .expression(Exp(.mod) {
Exp(.get) { "FLOW" }
360
})
return unclusteredLayer
}
@available(iOS 14.0, *)
private func createNumberLayer() -> SymbolLayer {
var numberLayer = SymbolLayer(id: Id.count, source: Id.source)
// check whether the point feature is clustered
numberLayer.filter = Exp(.has) { "point_count" }
// Display the value for 'point_count' in the text field
numberLayer.textField = .expression(Exp(.get) { "point_count" })
numberLayer.textSize = .constant(12)
return numberLayer
}
@available(iOS 14.0, *)
struct ClusteringExample_Preview: PreviewProvider {
static var previews: some View {
ClusteringExample()
}
}
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