Delete features (feature service)

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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 DeleteFeaturesViewController: UIViewController, AGSGeoViewTouchDelegate, AGSCalloutDelegate {
    @IBOutlet var mapView: AGSMapView! {
        didSet {
            mapView.map = AGSMap(basemapStyle: .arcGISStreets)
            // Set touch delegate on map view as self.
            mapView.touchDelegate = self
            mapView.callout.delegate = self
        }
    }

    /// The feature table to delete features from.
    var featureTable: AGSServiceFeatureTable!
    /// The service geodatabase that contains damaged property features.
    var serviceGeodatabase: AGSServiceGeodatabase!
    /// The feature layer created from the feature table.
    var featureLayer: AGSFeatureLayer!
    /// Last identify operation.
    var lastQuery: AGSCancelable!
    /// The currently selected feature.
    var selectedFeature: AGSFeature!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Add the source code button item to the right of navigation bar.
        (navigationItem.rightBarButtonItem as? SourceCodeBarButtonItem)?.filenames = ["DeleteFeaturesViewController"]

        // Load the service geodatabase.
        let damageFeatureService = URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/DamageAssessment/FeatureServer")!
        loadServiceGeodatabase(from: damageFeatureService)
    }

    /// Load and set a service geodatabase from a feature service URL.
    /// - Parameter serviceURL: The URL to the feature service.
    func loadServiceGeodatabase(from serviceURL: URL) {
        let serviceGeodatabase = AGSServiceGeodatabase(url: serviceURL)
        serviceGeodatabase.load { [weak self] error in
            guard let self = self else { return }
            if let error = error {
                self.presentAlert(error: error)
            } else {
                let featureTable = serviceGeodatabase.table(withLayerID: 0)!
                self.featureTable = featureTable
                self.serviceGeodatabase = serviceGeodatabase
                // Add the feature layer to the operational layers on map.
                let featureLayer = AGSFeatureLayer(featureTable: featureTable)
                self.featureLayer = featureLayer
                self.mapView.map?.operationalLayers.add(featureLayer)
                self.mapView.setViewpoint(AGSViewpoint(center: AGSPoint(x: 544871.19, y: 6806138.66, spatialReference: .webMercator()), scale: 2e6))
            }
        }
    }

    func showCallout(for feature: AGSFeature, at tapLocation: AGSPoint) {
        let title = feature.attributes["typdamage"] as! String
        mapView.callout.title = title
        mapView.callout.accessoryButtonImage = UIImage(named: "Discard")
        mapView.callout.show(for: feature, tapLocation: tapLocation, animated: true)
    }

    /// Delete a feature from the feature table.
    func deleteFeature(_ feature: AGSFeature) {
        featureTable.delete(feature) { [weak self] error in
            if let error = error {
                self?.presentAlert(message: "Error while deleting feature: \(error.localizedDescription)")
            } else {
                self?.applyEdits()
            }
        }
    }

    /// Apply local edits to the geodatabase.
    func applyEdits() {
        guard serviceGeodatabase.hasLocalEdits() else { return }
        serviceGeodatabase.applyEdits { [weak self] _, error in
            if let error = error {
                self?.presentAlert(message: "Error while applying edits: \(error.localizedDescription)")
            }
        }
    }

    // MARK: - AGSGeoViewTouchDelegate

    func geoView(_ geoView: AGSGeoView, didTapAtScreenPoint screenPoint: CGPoint, mapPoint: AGSPoint) {
        if let query = lastQuery { query.cancel() }
        // Hide the callout.
        mapView.callout.dismiss()

        lastQuery = mapView.identifyLayer(featureLayer, screenPoint: screenPoint, tolerance: 12, returnPopupsOnly: false) { [weak self] identifyLayerResult in
            guard let self = self else { return }
            self.lastQuery = nil
            if let feature = identifyLayerResult.geoElements.first as? AGSFeature {
                // Show callout for the feature.
                self.showCallout(for: feature, at: mapPoint)
                // Update selected feature.
                self.selectedFeature = feature
            } else if let error = identifyLayerResult.error {
                self.presentAlert(error: error)
            }
        }
    }

    // MARK: - AGSCalloutDelegate

    func didTapAccessoryButton(for callout: AGSCallout) {
        mapView.callout.dismiss()
        let alertController = UIAlertController(title: "Are you sure you want to delete the feature?", message: nil, preferredStyle: .alert)
        let alertAction = UIAlertAction(title: "Delete", style: .destructive) { [unowned self] _ in
            deleteFeature(selectedFeature)
        }
        alertController.addAction(alertAction)
        let cancelAlertAction = UIAlertAction(title: "Cancel", style: .cancel)
        alertController.addAction(cancelAlertAction)
        alertController.preferredAction = cancelAlertAction
        present(alertController, animated: true)
    }
}