Feature collection layer (query)

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Create a feature collection layer to show a query result from a service feature table.

Feature collection layer (query)

Use case

Consider a national wireless telecommunications company who wants to improve connectivity within areas of poor coverage. Their cell towers, cell tower radii and state boundaries data are held within service feature tables, which can be queried for states that don't meet a certain threshold of coverage. The query result can be used to create and display a single feature collection layer for analysis of areas requiring improved coverage.

How to use the sample

When launched, this sample displays a map with point features as a feature collection layer. Pan and zoom to explore the map.

How it works

  1. Perform a query using the AGSFeatureTable.queryFeatures(with:completion:) method on an AGSServiceFeatureTable.
  2. Create an AGSFeatureCollectionTable with the AGSFeatureQueryResult.
  3. Create an AGSFeatureCollection and add the feature collection table to it.
  4. Create an AGSFeatureCollectionLayer from the feature collection.
  5. Add the feature collection layer to the map's operationalLayers array.

Relevant API

  • AGSFeatureCollection
  • AGSFeatureCollectionLayer
  • AGSFeatureCollectionTable
  • AGSFeatureLayer
  • AGSFeatureQueryResult
  • AGSFeatureTable
  • AGSQueryParameters
  • AGSServiceFeatureTable

About the data

This application utilizes data from the wildfire feature service. It loads at full extent with features indicating wildfire response point features across the world.

Tags

layer, query, search, table

Sample Code

FeatureCollectionLayerQueryViewController.swift
                                                                       
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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 FeatureCollectionLayerQueryViewController: UIViewController {
    @IBOutlet var mapView: AGSMapView!

    private var featureTable: AGSServiceFeatureTable!

    override func viewDidLoad() {
        super.viewDidLoad()

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

        // initialize map with basemap
        let map = AGSMap(basemapStyle: .arcGISOceans)

        // assign map to the map view
        self.mapView.map = map

        // initialize service feature table to be queried
        self.featureTable = AGSServiceFeatureTable(url: URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Wildfire/FeatureServer/0")!)

        // create query parameters
        let queryParams = AGSQueryParameters()

        // 1=1 will give all the features from the table
        queryParams.whereClause = "1=1"

        // show progress hud
        UIApplication.shared.showProgressHUD(message: "Querying")

        // query feature from the table
        self.featureTable.queryFeatures(with: queryParams) { [weak self] (queryResult: AGSFeatureQueryResult?, error: Error?) in
            // hide progress hud
            UIApplication.shared.hideProgressHUD()

            if let error = error {
                // show error
                self?.presentAlert(error: error)
            } else {
                // create a feature collection table fromt the query results
                let featureCollectionTable = AGSFeatureCollectionTable(featureSet: queryResult!)

                // create a feature collection from the above feature collection table
                let featureCollection = AGSFeatureCollection(featureCollectionTables: [featureCollectionTable])

                // create a feature collection layer
                let featureCollectionLayer = AGSFeatureCollectionLayer(featureCollection: featureCollection)

                // add the layer to the operational layers array
                self?.mapView.map?.operationalLayers.add(featureCollectionLayer)
            }
        }
    }
}

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