Apply unique value renderer

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// Copyright 2023 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 ApplyUniqueValueRendererView: View {
    /// A map with topographic basemap centered on western United States.
    @State private var map: Map = {
        let map = Map(basemapStyle: .arcGISTopographic)

        // Center map on western United States
        let centerPoint = Point(x: -12356253.6, y: 3842795.4, spatialReference: .webMercator)
        map.initialViewpoint = Viewpoint(center: centerPoint, scale: 52681563.2)

        // Create a service feature table from the census feature service.
        let featureTable = ServiceFeatureTable(url: URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3")!)

        // Create a feature layer from the service feature table.
        let featureLayer = FeatureLayer(featureTable: featureTable)

        // Set a unique value renderer to the feature layer.
        featureLayer.renderer = makeUniqueValueRenderer()

        // Add the feature layer to the map.
        map.addOperationalLayer(featureLayer)

        return map
    }()

    /// Creates a unique value renderer configured to render the Pacific states
    /// as blue, the Mountain states as green, and the West South Central states
    /// as brown.
    /// - Returns: A `UniqueValueRenderer` object to be added to a featureLayer.
    private static func makeUniqueValueRenderer() -> UniqueValueRenderer {
        // Define a line symbol to use for the region fill symbol outlines.
        let stateOutlineSymbol = SimpleLineSymbol(style: .solid, color: .white, width: 0.7)

        // Define distinct fill symbols for the regions (use the same outline symbol).
        let pacificFillSymbol = SimpleFillSymbol(style: .solid, color: .blue, outline: stateOutlineSymbol)
        let mountainFillSymbol = SimpleFillSymbol(style: .solid, color: .green, outline: stateOutlineSymbol)
        let westSouthCentralFillSymbol = SimpleFillSymbol(style: .solid, color: .brown, outline: stateOutlineSymbol)

        // Create the unique values for each region.
        let pacificValue = UniqueValue(description: "Pacific Region", label: "Pacific", symbol: pacificFillSymbol, values: ["Pacific"])
        let mountainValue = UniqueValue(description: "Rocky Mountain Region", label: "Mountain", symbol: mountainFillSymbol, values: ["Mountain"])
        let westSouthCentralValue = UniqueValue(
            description: "West South Central Region",
            label: "West South Central",
            symbol: westSouthCentralFillSymbol,
            values: ["West South Central"]
        )

        // Create the default region fill symbol for regions not explicitly defined in the renderer.
        let defaultFillSymbol = SimpleFillSymbol(style: .cross, color: .gray)

        return UniqueValueRenderer(
            fieldNames: ["SUB_REGION"],
            uniqueValues: [pacificValue, mountainValue, westSouthCentralValue],
            defaultLabel: "Other",
            defaultSymbol: defaultFillSymbol
        )
    }

    var body: some View {
        // Create a map view to display the map.
        MapView(map: map)
    }
}

#Preview {
    ApplyUniqueValueRendererView()
}