Load WFS with XML query

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Load a WFS feature table using an XML query.

Load WFS with XML query sample

Use case

Runtime AGSQueryParameters objects can't represent all possible queries that can be made against a WFS feature service. For example, Runtime query parameters don't support wildcard searches. You can provide queries as raw XML strings, allowing you to access query functionality not available with AGSQueryParameters.

How to use the sample

Run the sample and view the data loaded from the the WFS feature table.

How it works

  1. Create an AGSWFSFeatureTable and an AGSFeatureLayer to visualize the table.
  2. Set the feature request mode to manualCache.
  3. Use populateFromService(withRequestXML:clearCache:completion:) to populate the table with only those features returned by the XML query.

Relevant API

  • AGSFeatureLayer
  • AGSWFSFeatureTable
  • AGSWFSFeatureTable.axisOrder
  • AGSWFSFeatureTable.populateFromService

About the data

This service shows trees in downtown Seattle and the surrounding area. An XML-encoded GetFeature request is used to limit results to only trees of the genus Tilia.

For additional information, see the underlying service on ArcGIS Online.

Tags

feature, OGC, query, service, web, WFS, XML

Sample Code

LoadWFSWithXMLQueryViewController.swift
                                                                                     
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//
// Copyright © 2019 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

/// A string containing the XML of the GetFeature request.
private let requestXML = """
    <wfs:GetFeature service="WFS" version="2.0.0"
    xmlns:Seattle_Downtown_Features="https://dservices2.arcgis.com/ZQgQTuoyBrtmoGdP/arcgis/services/Seattle_Downtown_Features/WFSServer"
    xmlns:wfs="http://www.opengis.net/wfs/2.0"
    xmlns:fes="http://www.opengis.net/fes/2.0"
    xmlns:gml="http://www.opengis.net/gml/3.2">
    <wfs:Query typeNames="Seattle_Downtown_Features:Trees">
    <fes:Filter>
    <fes:PropertyIsLike wildCard="*" escapeChar="\">
    <fes:ValueReference>Trees:SCIENTIFIC</fes:ValueReference>
    <fes:Literal>Tilia *</fes:Literal>
    </fes:PropertyIsLike>
    </fes:Filter>
    </wfs:Query>
    </wfs:GetFeature>
    """

/// A view controller that manages the interface of the Load WFS with XML Query
/// sample.
class LoadWFSWithXMLQueryViewController: UIViewController {
    /// The map view managed by the view controller.
    @IBOutlet var mapView: AGSMapView! {
        didSet {
            let featureTable = makeWFSFeatureTable()
            featureTable.populateFromService(withRequestXML: requestXML, clearCache: true) { [weak self, unowned featureTable] (_, _) in
                guard let extent = featureTable.extent else { return }
                self?.mapView.setViewpointGeometry(extent, padding: 50, completion: nil)
            }
            mapView.map = makeMap(featureTable: featureTable)
        }
    }

    /// Creates a WFS feature table.
    ///
    /// - Returns: A new `AGSWFSFeatureTable` object.
    func makeWFSFeatureTable() -> AGSWFSFeatureTable {
        let serviceURL = URL(string: "https://dservices2.arcgis.com/ZQgQTuoyBrtmoGdP/arcgis/services/Seattle_Downtown_Features/WFSServer?service=wfs&request=getcapabilities")!
        let tableName = "Seattle_Downtown_Features:Trees"
        let statesTable = AGSWFSFeatureTable(url: serviceURL, tableName: tableName)
        statesTable.axisOrder = .noSwap
        statesTable.featureRequestMode = .manualCache
        return statesTable
    }

    /// Creates a map with a feature layer from the given feature table.
    ///
    /// - Parameter featureTable: A feature table.
    /// - Returns: A new `AGSMap` object.
    func makeMap(featureTable: AGSFeatureTable) -> AGSMap {
        let map = AGSMap(basemapStyle: .arcGISNavigation)

        let featureLayer = AGSFeatureLayer(featureTable: featureTable)
        map.operationalLayers.add(featureLayer)

        return map
    }

    // MARK: UIViewController

    override func viewDidLoad() {
        super.viewDidLoad()

        (navigationItem.rightBarButtonItem as? SourceCodeBarButtonItem)?.filenames = ["LoadWFSWithXMLQueryViewController"]
    }
}

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