Find features in a feature table which match an SQL query.
Use case
Query expressions can be used in ArcGIS to select a subset of features from a feature table. This is most useful in large or complicated data sets. A possible use case might be on a feature table marking the location of street furniture through a city. A user may wish to query by a TYPE column to return "benches". In this sample, we query a U.S. state by STATE_NAME from a feature table containing all U.S. states.
How to use the sample
Input the name of a U.S. state into the text field. A query is performed and the matching features are highlighted or an error is returned.
How it works
- Create an
ServiceFeatureTable
using the URL of a feature service. - Create
QueryParameters
with awhereClause
specified. - Perform the query using
FeatureTable.queryFeatures(using:)
on the service feature table. - When complete, the query will return a
FeatureQueryResult
which can be iterated over to get the matching features.
Relevant API
- FeatureLayer
- FeatureQueryResult
- QueryParameters
- ServiceFeatureTable
About the data
This sample uses U.S. State polygon features from the USA 2016 Daytime Population feature service.
Tags
query, search
Sample Code
// Copyright 2023 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
//
// https://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 ArcGIS
import SwiftUI
struct QueryFeatureTableView: View {
@StateObject private var model = Model()
/// The error shown in the error alert.
@State private var error: Error?
/// The text in the search bar.
@State private var searchBarText = ""
var body: some View {
MapViewReader { mapViewProxy in
MapView(map: model.map)
.errorAlert(presentingError: $error)
// Makes the search bar.
.searchable(text: $searchBarText, prompt: Text("Search state names"))
.onSubmit(of: .search) {
model.currentQuery = searchBarText
}
// A task that runs when the query text changes.
.task(id: model.currentQuery) {
// Makes sure we have a query string.
guard !model.currentQuery.isEmpty else { return }
// Unselects all selected features.
model.featureLayer.clearSelection()
// Makes the query parameters and executes the query.
let queryParameters = QueryParameters()
queryParameters.whereClause = "upper(STATE_NAME) LIKE '%\(model.currentQuery.uppercased())%'"
do {
let queryResult = try await model.featureTable.queryFeatures(using: queryParameters)
let queryResultFeatures = Array(queryResult.features())
if !queryResultFeatures.isEmpty {
// Displays the selection.
model.featureLayer.selectFeatures(queryResultFeatures)
// Zooms to the selected features.
if let combinedExtent = GeometryEngine.combineExtents(of: queryResultFeatures.compactMap(\.geometry)) {
await mapViewProxy.setViewpointGeometry(combinedExtent, padding: 25)
}
} else {
// If the query returned no features then zooms
// to the extent of the layer.
if let layerExtent = model.featureLayer.fullExtent {
await mapViewProxy.setViewpointGeometry(layerExtent, padding: 50)
}
}
} catch {
// Displays the error as an alert.
self.error = error
}
}
}
}
}
private extension QueryFeatureTableView {
class Model: ObservableObject {
/// A map with a topographic basemap style.
let map: Map = {
let map = Map(basemapStyle: .arcGISTopographic)
map.initialViewpoint = Viewpoint(
center: Point(x: -11e6, y: 5e6, spatialReference: .webMercator),
scale: 9e7
)
return map
}()
/// The text used in the query.
@Published var currentQuery = ""
/// A feature table of US Daytime Population Census Tracts.
let featureTable = ServiceFeatureTable(
item: PortalItem(
portal: .arcGISOnline(connection: .anonymous),
id: .daytimePopulation
)
)
/// A feature layer created from the service feature table.
let featureLayer: FeatureLayer
init() {
// Creates a feature layer from feature table.
featureLayer = FeatureLayer(featureTable: featureTable)
// Shows the layer at all scales.
featureLayer.minScale = nil
featureLayer.maxScale = nil
// Sets a new renderer on the feature layer.
let lineSymbol = SimpleLineSymbol(style: .solid, color: .black, width: 1)
let fillSymbol = SimpleFillSymbol(style: .solid, color: .yellow.withAlphaComponent(0.5), outline: lineSymbol)
featureLayer.renderer = SimpleRenderer(symbol: fillSymbol)
// Adds the feature layer to the map.
map.addOperationalLayer(featureLayer)
}
}
}
private extension PortalItem.ID {
/// The portal item ID of a USA 2016 Daytime Population feature layer.
static var daytimePopulation: Self { Self("f01f0eda766344e29f42031e7bfb7d04")! }
}
#Preview {
NavigationStack {
QueryFeatureTableView()
}
}