Identify graphics

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// Copyright 2016 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 GOIdentifyViewController: UIViewController, AGSGeoViewTouchDelegate {
    @IBOutlet private weak var mapView: AGSMapView!

    private var map: AGSMap!
    private let graphicsOverlay = AGSGraphicsOverlay()

    override func viewDidLoad() {
        super.viewDidLoad()

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

        // initialize the map with topographic basemap
        self.map = AGSMap(basemapStyle: .arcGISTopographic)

        // call the method to add a graphics to the map view
        // will be using this graphic to test identify
        self.addGraphicsOverlay()

        // assign the map to the map view's map object
        self.mapView.map = self.map

        // add self as the touch delegate of the mapview
        // we will be using a method on the delegate to know
        // when the user tapped on the map view
        self.mapView.touchDelegate = self
    }

    func addGraphicsOverlay() {
        // polygon graphic
        let polygonGeometry = AGSPolygonBuilder(spatialReference: .webMercator())
        polygonGeometry.addPointWith(x: -20e5, y: 20e5)
        polygonGeometry.addPointWith(x: 20e5, y: 20e5)
        polygonGeometry.addPointWith(x: 20e5, y: -20e5)
        polygonGeometry.addPointWith(x: -20e5, y: -20e5)
        let polygonSymbol = AGSSimpleFillSymbol(style: AGSSimpleFillSymbolStyle.solid, color: .yellow, outline: nil)
        let polygonGraphic = AGSGraphic(geometry: polygonGeometry.toGeometry(), symbol: nil, attributes: nil)

        // assign the renderer
        self.graphicsOverlay.renderer = AGSSimpleRenderer(symbol: polygonSymbol)
        // add the polygon graphic
        self.graphicsOverlay.graphics.add(polygonGraphic)
        // add the graphics overlay to the map view
        self.mapView.graphicsOverlays.add(self.graphicsOverlay)
    }

    // MARK: - AGSGeoViewTouchDelegate

    func geoView(_ geoView: AGSGeoView, didTapAtScreenPoint screenPoint: CGPoint, mapPoint: AGSPoint) {
        // use the following method to identify graphics in a specific graphics overlay
        // otherwise if you need to identify on all the graphics overlay present in the map view
        // use `identifyGraphicsOverlaysAtScreenCoordinate:tolerance:maximumGraphics:completion:` method provided on map view
        let tolerance: Double = 12

        self.mapView.identify(self.graphicsOverlay, screenPoint: screenPoint, tolerance: tolerance, returnPopupsOnly: false, maximumResults: 10) { [weak self] (result: AGSIdentifyGraphicsOverlayResult) in
            if let error = result.error {
                print("error while identifying :: \(error.localizedDescription)")
            } else {
                // if a graphics is found then show an alert
                if !result.graphics.isEmpty {
                    self?.presentAlert(message: "Tapped on graphic")
                }
            }
        }
    }
}