Unique value renderer

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Render features in a layer using a distinct symbol for each unique attribute value.

Image of unique value renderer

Use case

A unique value renderer allows you to symbolize features in a layer based on one or more matching attributes. This is typically done by using unique colors, fill styles, or images to represent features with equal values in a string field. A unique value renderer could be used to show different types of trees on a vegetation map by using symbols corresponding to matching name attributes.

How to use the sample

The map with the symbolized feature layer will be shown automatically when the sample loads.

How it works

Using the AGSUniqueValueRenderer, separate symbols can be used to display features that have a specific value for a given field. In this case, the field is subregions of the USA. While multiple fields can be used, this sample only uses one.

  1. An AGSSimpleFillSymbol is defined for each type of feature.
  2. AGSSimpleFillSymbol can be applied to polygon features, which is the type of feature contained by this AGSServiceFeatureTable.
  3. Separate AGSUniqueValue objects are created which define the values in the renderer field and the symbol used to render matching features.
  4. A default symbol is created to render all features that do not match any of the AGSUniqueValue objects defined.

Relevant API

  • AGSFeatureLayer
  • AGSServiceFeatureTable
  • AGSSimpleFillSymbol
  • AGSSimpleLineSymbol
  • AGSUniqueValue
  • AGSUniqueValueRenderer

About the data

The map shows U.S. states symbolized by subregion. Symbols are defined for Pacific, Mountain, and West South Central states. All other features are symbolized with the default symbol.

Tags

draw, renderer, symbol, symbology, values

Sample Code

UniqueValueRendererViewController.swift
                                                                                                
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//
// Copyright 2016 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 view controller that manages the interface of the Unique Value Renderer
/// sample.
class UniqueValueRendererViewController: UIViewController {
    /// The map view managed by the view controller.
    @IBOutlet var mapView: AGSMapView! {
        didSet {
            // assign map to the map view
            mapView.map = makeMap()

            // set initial viewpoint
            let center = AGSPoint(x: -12966000.5, y: 4441498.5, spatialReference: .webMercator())
            mapView.setViewpoint(AGSViewpoint(center: center, scale: 4e7))
        }
    }

    /// Creates a map with a feature layer configured with a unique value
    /// renderer.
    ///
    /// - Returns: A new `AGSMap` object.
    func makeMap() -> AGSMap {
        // instantiate map with basemap
        let map = AGSMap(basemapStyle: .arcGISTopographic)

        // create feature layer
        let featureTable = AGSServiceFeatureTable(url: URL(string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3")!)
        let featureLayer = AGSFeatureLayer(featureTable: featureTable)

        // make unique value renderer and assign it to the feature layer
        featureLayer.renderer = makeUniqueValueRenderer()

        // add the layer to the map as operational layer
        map.operationalLayers.add(featureLayer)

        return map
    }

    /// Creates a unique value renderer configured to render California as red,
    /// Arizona as green, and Nevada as blue.
    ///
    /// - Returns: A new `AGSUniqueValueRenderer` object.
    func makeUniqueValueRenderer() -> AGSUniqueValueRenderer {
        // instantiate a new unique value renderer
        let renderer = AGSUniqueValueRenderer()

        // set the field to use for the unique values
        // You can add multiple fields to be used for the renderer in the form of a list, in this case we are only adding a single field
        renderer.fieldNames = ["STATE_ABBR"]

        // create symbols to be used in the renderer
        let defaultSymbol = AGSSimpleFillSymbol(style: .null, color: .clear, outline: AGSSimpleLineSymbol(style: .solid, color: .gray, width: 2))
        let californiaSymbol = AGSSimpleFillSymbol(style: .solid, color: .red, outline: AGSSimpleLineSymbol(style: .solid, color: .red, width: 2))
        let arizonaSymbol = AGSSimpleFillSymbol(style: .solid, color: .green, outline: AGSSimpleLineSymbol(style: .solid, color: .green, width: 2))
        let nevadaSymbol = AGSSimpleFillSymbol(style: .solid, color: .blue, outline: AGSSimpleLineSymbol(style: .solid, color: .blue, width: 2))

        // set the default symbol
        renderer.defaultSymbol = defaultSymbol
        renderer.defaultLabel = "Other"

        // create unique values
        let californiaValue = AGSUniqueValue(description: "State of California", label: "California", symbol: californiaSymbol, values: ["CA"])
        let arizonaValue = AGSUniqueValue(description: "State of Arizona", label: "Arizona", symbol: arizonaSymbol, values: ["AZ"])
        let nevadaValue = AGSUniqueValue(description: "State of Nevada", label: "Nevada", symbol: nevadaSymbol, values: ["NV"])

        // add the values to the renderer
        renderer.uniqueValues.append(contentsOf: [californiaValue, arizonaValue, nevadaValue])

        return renderer
    }

    // MARK: UIViewController

    override func viewDidLoad() {
        super.viewDidLoad()

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

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