Display a layer from a WFS service, requesting only features for the current extent.
Use case
WFS is an open standard with functionality similar to ArcGIS feature services. Runtime support for WFS allows you to interoperate with open systems, which are often used in inter-agency efforts, like those for disaster relief.
How to use the sample
Pan and zoom to see features within the current map extent.
How it works
Create an AGSWFSFeatureTable with a URL.
Set the feature request mode to manualCache.
Create an AGSFeatureLayer from the feature table and add it to the map.
Whenever map's view point is changed, use AGSWFSFeatureTable.populateFromService(with:clearCache:outFields:completion:) to load the table with data for the current visible extent.
Relevant API
AGSFeatureLayer
AGSGeoView.viewpointChangeHandler
AGSWFSFeatureTable
AGSWFSFeatureTable.populateFromService
About the data
This service shows building footprints for downtown Seattle. For additional information, see the underlying service on ArcGIS Online.
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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
classDisplayWFSViewController: UIViewController{
@IBOutletprivateweakvar mapView: AGSMapView!
privatevar wfsFeatureTable: AGSWFSFeatureTable!
privatevar lastQuery: AGSCancelable?
overridefuncviewDidLoad() {
super.viewDidLoad()
// Initialize a map with topographic basemaplet map =AGSMap(basemapStyle: .arcGISTopographic)
// A URL to the GetCapabilities endpoint of a WFS servicelet wfsServiceURL =URL(string: "https://dservices2.arcgis.com/ZQgQTuoyBrtmoGdP/arcgis/services/Seattle_Downtown_Features/WFSServer?service=wfs&request=getcapabilities")!// Name of the table to loadlet wfsTableName ="Seattle_Downtown_Features:Buildings"// Initialize a WFS feature table with service URL and uniquely identifying table name wfsFeatureTable =AGSWFSFeatureTable(url: wfsServiceURL, tableName: wfsTableName)
// Set feature request mode to manual - only manual is supported at v100.5.// In this mode, you must manually populate the table - panning and zooming won't request features automatically. wfsFeatureTable.featureRequestMode = .manualCache
// Initialize a feature layer from WFS feature tablelet wfsFeatureLayer =AGSFeatureLayer(featureTable: self.wfsFeatureTable)
// Create a simple rendererlet simpleLineSymbol =AGSSimpleLineSymbol(style: .solid, color: .red, width: 3.0)
let renderer =AGSSimpleRenderer(symbol: simpleLineSymbol)
// Apply renderer to feature layer wfsFeatureLayer.renderer = renderer
// Add feature layer to the map map.operationalLayers.add(wfsFeatureLayer)
// Query for features whenever map's viewpoint changesself.mapView.viewpointChangedHandler = { [weakself] inDispatchQueue.main.async {
self?.populateFeaturesFromQuery()
}
}
// Assign the map to the map view mapView.map = map
mapView.setViewpoint(AGSViewpoint(targetExtent: AGSEnvelope(xMin: -122.341581, yMin: 47.613758, xMax: -122.332662, yMax: 47.617207, spatialReference: .wgs84())))
// Add the source code button item to the right of navigation bar (navigationItem.rightBarButtonItem as!SourceCodeBarButtonItem).filenames = ["DisplayWFSViewController"]
}
privatefuncpopulateFeaturesFromQuery() {
// If there is an existing query request, cancel itiflet lastQuery =self.lastQuery {
lastQuery.cancel()
}
// Create query parameterslet params =AGSQueryParameters()
params.geometry =self.mapView.visibleArea?.extent
params.spatialRelationship = .intersects
// Show progressUIApplication.shared.showProgressHUD(message: "Querying")
// Populate features based on queryself.lastQuery =self.wfsFeatureTable.populateFromService(with: params, clearCache: true, outFields: ["*"]) { [weakself] (result: AGSFeatureQueryResult?, error: Error?) in// Check and get resultsiflet result = result {
// The resulting features should be displayed on the map// Print the count of featuresprint("Populated \(result.featureEnumerator().allObjects.count) features.")
}
// Check for error. If it's a user canceled error, do nothing.// Otherwise, display an alert.elseiflet error = error {
if (error asNSError).code !=NSUserCancelledError {
self?.presentAlert(error: error)
} else {
return }
}
// Hide ProgressUIApplication.shared.hideProgressHUD()
}
}
}