Change sublayer renderer

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// Copyright 2017 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
//
//   http://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 UIKit
import ArcGIS

class ChangeSublayerRendererViewController: UIViewController {
    @IBOutlet private var mapView: AGSMapView!
    @IBOutlet private var resetBarButtonItem: UIBarButtonItem!
    @IBOutlet private var applyRendererBarButtonItem: UIBarButtonItem!

    /// Map image layer.
    private let mapImageLayer = AGSArcGISMapImageLayer(url: URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer")!)
    /// The counties sublayer of the map image layer.
    private var countiesSublayer: AGSArcGISMapImageSublayer?
    private var originalRenderer: AGSRenderer?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Add the source code button item to the right of navigation bar.
        (self.navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["ChangeSublayerRendererViewController"]

        // Initialize map with basemap.
        let map = AGSMap(basemapStyle: .arcGISStreets)

        // Add map image layer to the map.
        map.operationalLayers.add(mapImageLayer)

        // Set map on the map view.
        mapView.map = map

        // Set viewpoint.
        let envelope = AGSEnvelope(xMin: -13834661.666904, yMin: 331181.323482, xMax: -8255704.998713, yMax: 9118038.075882, spatialReference: .webMercator())
        mapView.setViewpoint(AGSViewpoint(targetExtent: envelope))

        // Load map image layer to access sublayers.
        self.mapImageLayer.load { [weak self] (error: Error?) in
            guard let self = self else { return }
            if let error = error {
                print("Error loading map image layer: \(error)")
            } else {
                self.mapImageLayerDidLoad()
            }
        }
    }

    /// Called in response to the map image layer loading successfully.
    func mapImageLayerDidLoad() {
        // Get the counties sublayer.
        let mapImageSublayers = mapImageLayer.mapImageSublayers
        guard mapImageSublayers.count >= 3,
            let sublayer = mapImageSublayers[2] as? AGSArcGISMapImageSublayer else {
                return
        }
        countiesSublayer = sublayer
        // Load the sublayer to get the original renderer.
        sublayer.load { [weak self] (error) in
            guard let self = self else { return }
            if let error = error {
                print("Error loading map image sublayer: \(error)")
            } else {
                self.countiesSublayerDidLoad()
            }
        }
    }

    /// Called in response to the counties sublayer loading successfully.
    func countiesSublayerDidLoad() {
        originalRenderer = countiesSublayer?.renderer

        // Enable bar button items.
        applyRendererBarButtonItem.isEnabled = true
        resetBarButtonItem.isEnabled = true
    }

    /// Creates a class breaks renderer for counties in the US based on their
    /// population in 2007.
    ///
    /// - Returns: An `AGSClassBreaksRenderer` object.
    private func makeClassBreakRenderer() -> AGSClassBreaksRenderer {
        // Outline symbol.
        let lineSymbol = AGSSimpleLineSymbol(style: .solid, color: UIColor(white: 0.6, alpha: 1), width: 0.5)

        // Symbols for each class break.
        let symbol1 = AGSSimpleFillSymbol(style: .solid, color: UIColor(red: 0.89, green: 0.92, blue: 0.81, alpha: 1), outline: lineSymbol)
        let symbol2 = AGSSimpleFillSymbol(style: .solid, color: UIColor(red: 0.59, green: 0.76, blue: 0.75, alpha: 1), outline: lineSymbol)
        let symbol3 = AGSSimpleFillSymbol(style: .solid, color: UIColor(red: 0.38, green: 0.65, blue: 0.71, alpha: 1), outline: lineSymbol)
        let symbol4 = AGSSimpleFillSymbol(style: .solid, color: UIColor(red: 0.27, green: 0.49, blue: 0.59, alpha: 1), outline: lineSymbol)
        let symbol5 = AGSSimpleFillSymbol(style: .solid, color: UIColor(red: 0.16, green: 0.33, blue: 0.47, alpha: 1), outline: lineSymbol)

        // Class breaks.
        let classBreak1 = AGSClassBreak(description: "-99 to 8560", label: "-99 to 8560", minValue: -99, maxValue: 8560, symbol: symbol1)
        let classBreak2 = AGSClassBreak(description: "> 8,560 to 18,109", label: "> 8,560 to 18,109", minValue: 8561, maxValue: 18109, symbol: symbol2)
        let classBreak3 = AGSClassBreak(description: "> 18,109 to 35,501", label: "> 18,109 to 35,501", minValue: 18110, maxValue: 35501, symbol: symbol3)
        let classBreak4 = AGSClassBreak(description: "> 35,501 to 86,100", label: "> 35,501 to 86,100", minValue: 35502, maxValue: 86100, symbol: symbol4)
        let classBreak5 = AGSClassBreak(description: "> 86,100 to 10,110,975", label: "> 86,100 to 10,110,975", minValue: 86101, maxValue: 10110975, symbol: symbol5)

        // Create a class break renderer using the class breaks above.
        let classBreakRenderer = AGSClassBreaksRenderer(fieldName: "POP2007", classBreaks: [ classBreak1, classBreak2, classBreak3, classBreak4, classBreak5])

        return classBreakRenderer
    }

    // MARK: - Actions

    @IBAction private func applyRenderer() {
        countiesSublayer?.renderer = makeClassBreakRenderer()
    }

    @IBAction private func reset() {
        countiesSublayer?.renderer = originalRenderer
    }
}