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Showing content from https://developers.arcgis.com/swift/layers/tutorials/add-a-feature-layer-from-a-portal-item/ below:

Add a feature layer from a portal item | ArcGIS Maps SDK for Swift

Learn how to use an ArcGIS portal item to access and display a feature layer in a map.

You can host a variety of geographic data and other resources using ArcGIS Online. These portal items can also define how the data is presented. A web map or web scene, for example, not only defines the layers for a map or scene, but also how layers are symbolized, the minimum and/or maximum scales at which they display, and several other properties. Likewise, a hosted feature layer contains the data for the layer and also defines the symbols and other display properties for how it is presented. When you add a map, scene, or layer from a portal item to your app, everything that has been saved with the item is applied in your app. Adding portal items to your app rather than creating them programmatically saves you from writing a lot of code, and can provide consistency across apps that use the same data.

In this tutorial, you will add a hosted feature layer to display trailheads in the Santa Monica Mountains of Southern California. The hosted layer defines the trailhead locations (points) as well as the symbols used to display them.

Prerequisites

Before starting this tutorial:

You need an ArcGIS Location Platform or ArcGIS Online account.
Your system meets the system requirements.

Develop or Download

You have two options for completing this tutorial:

Option 1: Develop the code

To start the tutorial, complete the Display a map tutorial. This creates a map to display the Santa Monica Mountains in California using the topographic basemap from the ArcGIS Basemap Styles service.

Open an Xcode project

Open the .xcodeproj project you created by completing the Display a map tutorial.
Continue with the following instructions to use an ArcGIS portal item to access and display a feature layer in a map.

Add a feature layer to the map

Open the ContentView.swift file and update the map object. Create a PortalItem object referencing the feature layer by passing in the portal and item ID.

Each portal item has a unique Item.ID, identified from its URL on ArcGIS Online.

In your browser, go to the Trailheads Styled layer on ArcGIS Online and find the item ID at the end of the URL. It should be 2e4b3df6ba4b44969a3bc9827de746b3.

The feature layer referenced with this portal item contains trailheads in and around the Santa Monica Mountains.

ContentView.swift

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    @State private var map = {
        // Creates a map with the topographic basemap style.
        let map = Map(basemapStyle: .arcGISTopographic)
        // Sets the initial viewpoint to Malibu, California.
        map.initialViewpoint = Viewpoint(latitude: 34.027, longitude: -118.805, scale: 72_000)

        // Creates an anonymous portal item pointing to https://www.arcgis.com with an item ID.
        let portalItem = PortalItem(
            portal: .arcGISOnline(connection: .anonymous),
            id: Item.ID("2e4b3df6ba4b44969a3bc9827de746b3")!
        )

        return map
    }()

Create a FeatureLayer object from the portal item and a layer ID. The layer ID uniquely identifies one of the layers from the portal item. Add the layer to the map's operational layers.

A layer ID is required because a portal item may have more than one layer. For instance, when a feature service has 3 layers - trailheads (points), trails (polylines) and trail areas (polygons), the corresponding portal item would contain all three layers.

ContentView.swift

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    @State private var map = {
        // Creates a map with the topographic basemap style.
        let map = Map(basemapStyle: .arcGISTopographic)
        // Sets the initial viewpoint to Malibu, California.
        map.initialViewpoint = Viewpoint(latitude: 34.027, longitude: -118.805, scale: 72_000)

        // Creates an anonymous portal item pointing to https://www.arcgis.com with an item ID.
        let portalItem = PortalItem(
            portal: .arcGISOnline(connection: .anonymous),
            id: Item.ID("2e4b3df6ba4b44969a3bc9827de746b3")!
        )

        // Creates a feature layer from the portal item and a layer ID.
        let layer = FeatureLayer(featureServiceItem: portalItem, layerID: 0)
        // Adds the layer to the map's operational layers.
        map.addOperationalLayer(layer)

        return map
    }()

Run the solution

Press Command + R to run the app.

If you are using the Xcode simulator your system must meet these minimum requirements: macOS 14 (Sonoma), Xcode 16, iOS 18. If you are using a physical device, then refer to the system requirements.

You should see a map of trail heads in the Santa Monica mountains. Tap, drag, and zoom on the map view to explore the map.

Alternatively, you can download the tutorial solution, as follows.

Option 2: Download the solution

Click the Download solution link under Solution and unzip the file to a location on your machine.
Open the .xcodeproj file in Xcode.

Since the downloaded solution does not contain authentication credentials, you must first set up authentication to create credentials, and then add the developer credentials to the solution.

Set developer credentials in the solution

To access the secure ArcGIS location services used in this tutorial, you must implement API key authentication or user authentication using an ArcGIS Location Platform or an ArcGIS Online account.

You can implement API key authentication or user authentication in this tutorial. Compare the differences below:

API key authentication

Users are not required to sign in.
Requires creating an API key credential with the correct privileges.
API keys are long-lived access tokens.
Service usage is billed to the API key owner/developer.
Simplest authentication method to implement.
Recommended approach for new ArcGIS developers.

Learn more in API key authentication.

User authentication

Users are required to sign in with an ArcGIS account.
User accounts must have privilege to access the ArcGIS services used in application.
Requires creating OAuth credentials.
Application uses a redirect URL and client ID.
Service usage is billed to the organization of the user signed into the application.

Learn more in User authentication.

Security and authentication guide

To learn more about the different types of authentication, visit Types of authentication.

Create a new API key access token with privileges to access the secure resources used in this tutorial.

Complete the Create an API key tutorial and create an API key with the following privilege(s):
- Privileges
  - Location services > Basemaps
Copy and paste the API key access token into a safe location. It will be used in a later step.

Create new OAuth credentials to access the secure resources used in this tutorial.

Complete the Create OAuth credentials for user authentication tutorial to obtain a Client ID and Redirect URL.

A Client ID uniquely identifies your app on the authenticating server. If the server cannot find an app with the provided Client ID, it will not proceed with authentication.

The Redirect URL (also referred to as a callback url) is used to identify a response from the authenticating server when the system returns control back to your app after an OAuth login. Since it does not necessarily represent a valid endpoint that a user could navigate to, the redirect URL can use a custom scheme, such as my-app://auth. It is important to make sure the redirect URL used in your app's code matches a redirect URL configured on the authenticating server.
Copy and paste the Client ID and Redirect URL into a safe location. They will be used in a later step.

All users that access this application need account privileges to access the ArcGIS Basemap Styles service.

Set developer credentials

To allow your app users to access ArcGIS location services, use the developer credentials that you created in the Set up authentication step to authenticate requests for resources.

Pass your API Key access token to the ArcGISEnvironment.

In the Project Navigator, click MainApp.swift.

Set the AuthenticationMode to .apiKey.

MainApp.swift

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    // Change the `AuthenticationMode` to `.apiKey` if your application uses API key authentication.

    private var authenticationMode: AuthenticationMode { .apiKey }

Set the apiKey property with your API key access token.

MainApp.swift

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    // Please enter an API key access token if your application uses API key authentication.

    private let apiKey = APIKey("<#YOUR-ACCESS-TOKEN#>")

Best Practice: The access token is stored directly in the code as a convenience for this tutorial. Do not store credentials directly in source code in a production environment.

Use the Authenticator toolkit component to manage your OAuth credentials and pass it to the ArcGISEnvironment.

In the Project Navigator, click MainApp.swift.

Set the AuthenticationMode to .user.

MainApp.swift

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// Change the `AuthenticationMode` to `.user` if your application uses OAuth credentials.

private var authenticationMode: AuthenticationMode { .user }

Set your portalURL, clientID and redirectURL values.

MainApp.swift

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    // Setup an `Authenticator` with OAuth configuration if your application uses OAuth credentials.
    @ObservedObject var authenticator = Authenticator(
        oAuthUserConfigurations: [
            OAuthUserConfiguration(

                // Please enter OAuth credentials for user authentication.

                portalURL: URL(string: "<#YOUR-PORTAL-URL#>")!,
                clientID: "<#YOUR-CLIENT-ID#>",
                redirectURL: URL(string: "<#YOUR-REDIRECT-URL#>")!

            )
        ]
    )

Best Practice: The OAuth credentials are stored directly in the code as a convenience for this tutorial. Do not store credentials directly in source code in a production environment.

Run the solution

Press Command + R to run the app.

You should see a map of trail heads in the Santa Monica mountains. Tap, drag, and zoom on the map view to explore the map.

What's next?

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

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