Style a feature layer

Learn how to apply renderers and label definitions to a feature layer based on attribute values.

style a feature layer

Applications can display feature layer data with different styles to enhance the visualization. The type of Renderer you choose depends on your application. A SimpleRenderer applies the same symbol to all features, a UniqueValueRenderer applies a different symbol to each unique attribute value, and a ClassBreaksRenderer applies a symbol to a range of numeric values. Renderers are responsible for accessing the data and applying the appropriate symbol to each feature when the layer draws. You can also use a LabelDefinition to show attribute information for features. Visit the Styles and data visualization documentation to learn more about styling layers.

You can also author, style and save web maps, web scenes, and layers as portal items and then add them to the map in your application. Visit the following tutorials to learn more about adding portal items.

In this tutorial, you will apply different renderers to enhance the visualization of three feature layers with data for the Santa Monica Mountains: Trailheads with a single symbol, Trails based on elevation change and bike use, and Parks and Open Spaces based on the type of park.

Prerequisites

The following are required for this tutorial:

An ArcGIS account to access your API keys. If you don't have an account, sign up for free.
Your system meets the system requirements.

Steps

Open the Xcode project

To start the tutorial, complete the Display a map tutorial or download and unzip the solution.
Open the .xcodeproj file in Xcode.
If you downloaded the solution project, set your API key.
An API Key enables access to services, web maps, and web scenes hosted in ArcGIS Online.
1. Go to your developer dashboard to get your API key. For these tutorials, use your default API key. It is scoped to include all of the services demonstrated in the tutorials.
2. In Xcode, in the Project Navigator, click MainApp.swift.
3. In the Editor, set the ArcGISEnvironment.apiKey property on the ArcGISEnvironment with your API key.
MainApp.swift
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 import SwiftUI import ArcGIS @main struct MainApp: App { init() { ArcGISEnvironment.apiKey = APIKey("<#your-API-key#>") } var body: some SwiftUI.Scene { WindowGroup { ContentView() .ignoresSafeArea() } } }

Add app configuration constants

Create a configuration file to specify constants that can be used by the app to connect to data and resources.

Add a new swift file named AppConfiguration.swift.
- In Xcode's app menu, select File > New > File....
- Select Swift File from the iOS tab's Source sub-menu.
- Name the file AppConfiguration and ensure your app's target is checked.
- Click Create.

Create five static URLs: four for accessing feature layers, and a fifth for accessing a static image for use in a picture marker symbol. You will use these resources in future steps.

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extension URL {
    static let bikesTrails = URL(string: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails/FeatureServer/0")!
    static let parksAndOpenSpaces = URL(string: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space/FeatureServer/0")!
    static let trails = URL(string: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails/FeatureServer/0")!
    static let trailheads = URL(string: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0")!
    static let trailheadImage = URL(string: "https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png")!
}

Create helper method to make a feature layer

Add a helper method that creates a feature layer from a given URL.

Open ContentView.swift in the Project Navigator. Add a new method named makeFeatureLayer(url: URL).

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    private func makeFeatureLayer(url: URL) -> FeatureLayer {
        let serviceFeatureTable = ServiceFeatureTable(url: url)
        let featureLayer = FeatureLayer(featureTable: serviceFeatureTable)
        return featureLayer
    }

Add a layer with a unique value renderer

Create a method to apply a different symbol for each type of park area to the Parks and Open Spaces feature layer.

Add a new method named makeOpenSpaceLayer() in ContentView.swift.

UniqueValue assigns a symbol to a value or values. A unique value renderer uses a collection of unique values to assign the appropriate symbol for each feature it renderers.

For this example, the renderer uses a feature's TYPE attribute value to apply the correct symbol.

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    private func makeOpenSpaceLayer() {
        // Creates a parks and open spaces feature layer.
        let featureLayer = makeFeatureLayer(url: .parksAndOpenSpaces)
        // Creates fill symbols.
        let purpleFillSymbol = SimpleFillSymbol(style: .solid, color: .purple, outline: .none)
        let greenFillSymbol = SimpleFillSymbol(style: .solid, color: .green, outline: .none)
        let blueFillSymbol = SimpleFillSymbol(style: .solid, color: .blue, outline: .none)
        let redFillSymbol = SimpleFillSymbol(style: .solid, color: .red, outline: .none)

        // Creates a unique value for natural areas, regional open spaces, local parks & regional recreation parks.
        let naturalAreas = UniqueValue(description: "Natural Areas", label: "Natural Areas", symbol: purpleFillSymbol, values: ["Natural Areas"])
        let regionalOpenSpace = UniqueValue(description: "Regional Open Space", label: "Regional Open Space", symbol: greenFillSymbol, values: ["Regional Open Space"])
        let localPark = UniqueValue(description: "Local Park", label: "Local Park", symbol: blueFillSymbol, values: ["Local Park"])
        let regionalRecreationPark = UniqueValue(description: "Regional Recreation Park", label: "Regional Recreation Park", symbol: redFillSymbol, values: ["Regional Recreation Park"])

        // Creates and assigns a unique value renderer to the feature layer.
        let openSpacesUniqueValueRenderer = UniqueValueRenderer(fieldNames: ["TYPE"], uniqueValues: [naturalAreas, regionalOpenSpace, localPark, regionalRecreationPark], defaultLabel: "Open Spaces", defaultSymbol: .none)
        featureLayer.renderer = openSpacesUniqueValueRenderer

        // Sets the layer opacity to semi-transparent.
        featureLayer.opacity = 0.2
        // Adds the feature layer to the map.
        map.addOperationalLayer(featureLayer)
    }

Update the MapView task to call the new makeOpenSpaceLayer() method.

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        // Displays the map.
        MapView(map: map)
            .task {

                makeOpenSpaceLayer()

            }

Press <Command+R> to run the app.

When the app opens, Parks and Open Spaces feature layer is added to the map. The map displays the different types of parks and open spaces with four unique symbols.

Add a layer with a class breaks renderer

Create a method to apply a different symbol for each of the five ranges of elevation gain to the Trails feature layer.

Add a new method named addTrailsLayer().

A ClassBreak assigns a symbol to a range of values.

For this example, the renderer uses each feature's ELEV_GAIN attribute value to classify it into a defined range (class break) and apply the corresponding symbol.

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    private func addTrailsLayer() {
        // Creates a trails feature layer.
        let featureLayer = makeFeatureLayer(url: .trails)

        // Creates simple line symbols.
        let firstClassSymbol = SimpleLineSymbol(style: .solid, color: .purple, width: 3.0)
        let secondClassSymbol = SimpleLineSymbol(style: .solid, color: .purple, width: 4.0)
        let thirdClassSymbol = SimpleLineSymbol(style: .solid, color: .purple, width: 5.0)
        let fourthClassSymbol = SimpleLineSymbol(style: .solid, color: .purple, width: 6.0)
        let fifthClassSymbol = SimpleLineSymbol(style: .solid, color: .purple, width: 7.0)

        // Creates 5 class breaks.
        let firstClassBreak = ClassBreak(description: "Under 500", label: "0 - 500", minValue: 0.0, maxValue: 500.0, symbol: firstClassSymbol)
        let secondClassBreak = ClassBreak(description: "501 to 1000", label: "501 - 1000", minValue: 501.0, maxValue: 1000.0, symbol: secondClassSymbol)
        let thirdClassBreak = ClassBreak(description: "1001 to 1500", label: "1001 - 1500", minValue: 1001.0, maxValue: 1500.0, symbol: thirdClassSymbol)
        let fourthClassBreak = ClassBreak(description: "1501 to 2000", label: "1501 - 2000", minValue: 1501.0, maxValue: 2000.0, symbol: fourthClassSymbol)
        let fifthClassBreak = ClassBreak(description: "2001 to 2300", label: "2001 - 2300", minValue: 2001.0, maxValue: 2300.0, symbol: fifthClassSymbol)
        let elevationBreaks = [firstClassBreak, secondClassBreak, thirdClassBreak, fourthClassBreak, fifthClassBreak]

        // Creates and assigns a class breaks renderer to the feature layer.
        let elevationClassBreaksRenderer = ClassBreaksRenderer(fieldName: "ELEV_GAIN", classBreaks: elevationBreaks)
        featureLayer.renderer = elevationClassBreaksRenderer

        // Sets the layer opacity to semi-transparent.
        featureLayer.opacity = 0.75
        // Adds the feature layer to the map.
        map.addOperationalLayer(featureLayer)
    }

Update the MapView task to call the new addTrailsLayer() method.

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        // Displays the map.
        MapView(map: map)
            .task {

                makeOpenSpaceLayer()

                addTrailsLayer()

            }

Press <Command+R> to run the app.

When the app opens, the Trails feature layer is added to the map. The map displays trails with different symbols depending on trail elevation.

Add layers with definition expressions

You can use a definition expression to define a subset of features to display. Features that do not meet the expression criteria are not displayed by the layer. In the following steps, you will create two methods that use a definition expression to apply a symbol to a subset of features in the Trails feature layer.

FeatureLayer.definitionExpression uses a SQL expression to limit the features available for query and display. Your code will create two layers that each display a different subset of trails based on the value for the `USE_BIKE` field. Trails that allow bikes will be symbolized with a blue symbol (`"USE_BIKE = 'Yes'"`) and those that don't will be red (`"USE_BIKE = 'No'"`). Another way to symbolize these features would be to create a UniqueValueRenderer that applies a different symbol for these values.

Add a method with a definition expression to filter for trails that permit bikes.

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    private func addBikeOnlyTrailsLayer() {
        // Creates a trails feature layer.
        let featureLayer = makeFeatureLayer(url: .bikesTrails)

        // Writes a definition expression to filter for trails that do permit the use of bikes.
        featureLayer.definitionExpression = "USE_BIKE = 'Yes'"

        // Creates and assigns a simple renderer to the feature layer.
        let bikeTrailSymbol = SimpleLineSymbol(style: .dot, color: .blue, width: 2.0)
        let bikeTrailRenderer = SimpleRenderer(symbol: bikeTrailSymbol)
        featureLayer.renderer = bikeTrailRenderer
        // Adds the feature layer to the map.
        map.addOperationalLayer(featureLayer)
    }

Add another method with a definition expression to filter for trails that don't allow bikes.

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    private func addNoBikeTrailsLayer() {
        // Creates a no bike trails feature layer.
        let featureLayer = makeFeatureLayer(url: .bikesTrails)
        // Writes a definition expression to filter for trails that don't permit the use of bikes.
        featureLayer.definitionExpression = "USE_BIKE = 'No'"

        // Creates and assigns a simple renderer to the feature layer.
        let noBikeTrailSymbol = SimpleLineSymbol(style: .dot, color: .red, width: 2.0)
        let noBikeTrailRenderer = SimpleRenderer(symbol: noBikeTrailSymbol)
        featureLayer.renderer = noBikeTrailRenderer
        // Adds the feature layer to the map.
        map.addOperationalLayer(featureLayer)
    }

Update the MapView task to call the new addBikeOnlyTrailsLayer() and addNoBikeTrailsLayer() methods.

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        // Displays the map.
        MapView(map: map)
            .task {

                makeOpenSpaceLayer()

                addTrailsLayer()

                addNoBikeTrailsLayer()
                addBikeOnlyTrailsLayer()

            }

Press <Command+R> to run the app.

When the app opens, two Trails feature layers are added to the map. One shows where bikes are permitted and the other where they are prohibited.

Add a layer with a label definition

Create a method to style trailheads with hiker images and labels for the Trailheads feature layer.

Create a helper method named makeLabelDefinition() to define a label definition based on a specific attribute of the feature layer TRL_NAME. Also define label placement and symbol.

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    private func makeLabelDefinition() -> LabelDefinition {
        let trailHeadsTextSymbol = TextSymbol()
        trailHeadsTextSymbol.color = .white
        trailHeadsTextSymbol.size = 20.0
        trailHeadsTextSymbol.haloColor = .red
        trailHeadsTextSymbol.haloWidth = 2.0
        trailHeadsTextSymbol.fontFamily = "Noto Sans"
        trailHeadsTextSymbol.fontStyle = .italic
        trailHeadsTextSymbol.fontWeight = .normal

        // Makes an arcade label expression.
        let expression = "$feature.TRL_NAME"
        let arcadeLabelExpression = ArcadeLabelExpression(arcadeString: expression)
        let labelDefinition = LabelDefinition(labelExpression: arcadeLabelExpression, textSymbol: trailHeadsTextSymbol)
        labelDefinition.placement = .pointAboveCenter

        return labelDefinition
    }

Add a method named addTrailheadsLayer().

Use a PictureMarkerSymbol to draw a trailhead hiker image. Use the LabelDefinition to label each trailhead by its name.

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    private func addTrailheadsLayer() {
        // Creates a trailheads feature layer.
        let featureLayer = makeFeatureLayer(url: .trailheads)

        let pictureMarkerSymbol = PictureMarkerSymbol(url: .trailheadImage)
        pictureMarkerSymbol.height = 18.0
        pictureMarkerSymbol.width = 18.0
        let simpleRenderer = SimpleRenderer(symbol: pictureMarkerSymbol)
        featureLayer.renderer = simpleRenderer
        featureLayer.labelsAreEnabled = true
        let trailHeadsDefinition = makeLabelDefinition()
        featureLayer.addLabelDefinition(trailHeadsDefinition)
        // Adds the feature layer to the map.
        map.addOperationalLayer(featureLayer)
    }

Update the MapView task to call the new addTrailheadsLayer() method.

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        // Displays the map.
        MapView(map: map)
            .task {

                makeOpenSpaceLayer()

                addTrailsLayer()

                addNoBikeTrailsLayer()
                addBikeOnlyTrailsLayer()

                addTrailheadsLayer()

            }

Press <Command+R> to run the app.
If you are using the Xcode simulator your system must meet these minimum requirements: macOS Monterey 12.5, Xcode 14.0, iOS 16. If you are using a physical device, then refer to the system requirements.

When the app opens, all the layers you've created and symbolized are displayed on the map.

Parks and open spaces are displayed with four unique symbols
Trails use different symbols (line widths) depending on trail elevation
Trails are blue where bikes are permitted and red where they are prohibited
Trailheads are displayed with a hiker icon and labels display each trail's name

What's next?

Learn how to use additional API features, ArcGIS location services, and ArcGIS tools in these tutorials:

Display a web map

ArcGIS Maps SDK for Swift

Style a feature layer

Solution

Estimated time

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