Query map image sublayer

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
// Copyright 2025 Esri
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import ArcGIS
import SwiftUI

struct QueryMapImageSublayerView: View {
    /// The view model for this sample.
    @State private var model = Model()

    /// The current viewpoint of the map view.
    @State private var viewpoint: Viewpoint? = .westernUSA

    /// A Boolean value indicating whether there is an ongoing query operation.
    @State private var isQuerying = false

    /// The minimum population value in the text field.
    @State private var minimumPopulation: Int?

    /// The error shown in the error alert.
    @State private var error: Error?

    var body: some View {
        MapView(map: model.map, viewpoint: viewpoint, graphicsOverlays: [model.graphicsOverlay])
            .onViewpointChanged(kind: .boundingGeometry) { viewpoint = $0 }
            .overlay(alignment: .top) {
                LabeledContent("Minimum population") {
                    TextField("1,000,000", value: $minimumPopulation, format: .number)
                        .multilineTextAlignment(.trailing)
                }
                .padding(8)
                .background(Color.primary.colorInvert())
                .clipShape(.rect(cornerRadius: 5))
                .shadow(radius: 50)
                .padding()
            }
            .toolbar {
                ToolbarItem(placement: .bottomBar) {
                    Button("Query") {
                        isQuerying = true
                    }
                    .disabled(isQuerying || minimumPopulation == nil || viewpoint == nil)
                    .task(id: isQuerying) {
                        guard isQuerying, let minimumPopulation, let viewpoint else {
                            return
                        }
                        defer { isQuerying = false }

                        do {
                            try await model.queryMapImageSublayers(
                                minimumPopulation: minimumPopulation,
                                geometry: viewpoint.targetGeometry
                            )
                        } catch {
                            self.error = error
                        }
                    }
                }
            }
            .task {
                // Sets up the sublayers when the sample appears.
                do {
                    try await model.setUpMapImageSublayers()
                } catch {
                    self.error = error
                }
            }
            .errorAlert(presentingError: $error)
    }
}

/// The view model for this sample.
@MainActor
private final class Model {
    /// A map with a streets basemap.
    let map = Map(basemapStyle: .arcGISStreets)

    /// The graphics overlay for the query result graphics.
    let graphicsOverlay = GraphicsOverlay()

    /// The map image sublayers to query.
    private var mapImageSublayers: [ArcGISMapImageSublayer] = []

    /// The sublayer names and corresponding symbol that will be used for the
    /// layers' query result graphics.
    private let sublayerGraphicSymbols: [String: Symbol] = {
        let citiesSymbol = SimpleMarkerSymbol(style: .circle, color: .red, size: 16)

        let countyOutline = SimpleLineSymbol(style: .dash, color: .cyan, width: 2)
        let countySymbol = SimpleFillSymbol(style: .diagonalCross, color: .cyan, outline: countyOutline)

        let darkCyan = UIColor(red: 0, green: 0.55, blue: 0.55, alpha: 1)
        let stateOutline = SimpleLineSymbol(style: .solid, color: darkCyan, width: 6)
        let stateSymbol = SimpleFillSymbol(style: .noFill, color: .cyan, outline: stateOutline)

        return ["Cities": citiesSymbol, "Counties": countySymbol, "States": stateSymbol]
    }()

    /// Sets up the map image sublayers used by this sample.
    func setUpMapImageSublayers() async throws {
        // Creates a map image layer and adds it to the map.
        let mapImageLayer = ArcGISMapImageLayer(url: .usaMapService)
        map.addOperationalLayer(mapImageLayer)

        // Loads the layer and its map image sublayers.
        try await mapImageLayer.load()
        await mapImageLayer.mapImageSublayers.load()

        // Gets the sublayers containing the field we will be querying (POP2000).
        mapImageSublayers = mapImageLayer.mapImageSublayers.filter { sublayer in
            sublayer.table?.field(named: "POP2000") != nil
        }
    }

    /// Queries the map image sublayers and adds graphics for the resulting features.
    /// - Parameters:
    ///   - minimumPopulation: The minimum population a feature must have to be
    ///   included in the results.
    ///   - geometry: The geometry to query within.
    func queryMapImageSublayers(minimumPopulation: Int, geometry: Geometry) async throws {
        // Removes all the graphics to have a fresh start.
        graphicsOverlay.removeAllGraphics()

        // Creates parameters to query for features with a population greater than the minimum.
        let queryParameters = QueryParameters()
        queryParameters.whereClause = "POP2000 > \(minimumPopulation)"
        queryParameters.geometry = geometry

        await withThrowingTaskGroup(of: Void.self) { group in
            for sublayer in mapImageSublayers {
                group.addTask { [weak self] in
                    // Queries the sublayer's table using the parameters.
                    let result = try await sublayer.table!.queryFeatures(using: queryParameters)

                    // Creates a graphic for each feature in the result.
                    let symbol = self?.sublayerGraphicSymbols[sublayer.name]
                    let graphics = result.features().map { feature in
                        let graphic = Graphic(geometry: feature.geometry, symbol: symbol)
                        // Sets the Z-index for consistent draw order.
                        graphic.zIndex = -sublayer.id
                        return graphic
                    }

                    // Adds the graphics to the overlay.
                    self?.graphicsOverlay.addGraphics(graphics)
                }
            }
        }
    }
}

private extension Viewpoint {
    /// A viewpoint centered on the western United States.
    static var westernUSA: Viewpoint {
        .init(
            boundingGeometry: Envelope(
                xRange: -13_933_000 ... -12_071_000,
                yRange: 3_387_000 ... 6_701_000,
                spatialReference: .webMercator
            )
        )
    }
}

private extension URL {
    /// A web URL to a "USA" map server containing sample data for the United States.
    static var usaMapService: URL {
        URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer")!
    }
}

#Preview {
    QueryMapImageSublayerView()
}