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OpenFeature Provider for iOS SDK

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Integrate your iOS applications with Harness FME using the iOS OpenFeature ProviderAn OpenFeature Provider wraps the Harness FME SDK, acting as a bridge between the OpenFeature SDK and the FME SDK. It translates OpenFeature function calls into operations handled by the FME SDK., a standardized, vendor-agnostic feature flagging API. This provider implements the OpenFeature specification and bridges the OpenFeature SDK with the Harness FME iOS SDK.

This page walks you through installing, configuring, and using the iOS OpenFeature provider to evaluate feature flagsA conditional toggle that wraps a section of code, enabling it to be selectively turned on or off remotely (down to an individual user) without a new code deployment. Feature flags decouple deploys from releases and support canary rollouts, A/B testing, and instant kill switches. in your iOS applications.

Before you begin​

Before you begin, ensure you have the following:

  • A valid Harness FME SDK key for your project
  • An iOS project (Xcode 14+)
  • Access to your project's Package.swift file or Xcode project to add the provider dependency

Version compatibility​

ComponentMinimum Version
iOS≥ 14
@splitsoftware/split-openfeature-provider-swift≥ 1.0.0
OpenFeature Swift SDK≥ 0.4.0

Install the provider and dependencies​

Add the Harness FME OpenFeature provider dependency to your application's Xcode project using Swift Package Manager.

.package(url: "https://github.com/splitio/split-openfeature-provider-swift", from: "1.0.0")

Initialize the provider​

The Harness FME OpenFeature provider requires an iOS application Context (for SDK initialization) and your Harness FME SDK Key.

import Split
import Combine
import OpenFeature
import SplitProvider

Task {

    var providerCancellable: AnyCancellable?
    let provider = SplitProvider(key: "API_KEY")
    
    // Setup events observer
    providerCancellable = OpenFeatureAPI.shared.observe().sink { [weak self] event in
        switch event {
            case .ready:
                print("Split Provider is ready")
            case .error(let message):
                print("Split Provider error:", message)
            default:
                break
        }
    }
    
    // Setup OpenFeature with initial context
    let context = ImmutableContext(targetingKey: "user_key")
    await OpenFeatureAPI.shared.setProviderAndWait(provider: provider, initialContext: context)
    
    // Get a client and evaluate a flag
    let client = OpenFeatureAPI.getClient()
    let flagEvaluationResult = client.getBooleanValue("new-feature", false)
}

Construct an evaluation context​

Provide an evaluation contextThe Evaluation Context holds contextual information used during flag evaluation. It can include static data (like application or host identifiers) and dynamic data (such as a client IP address), which can be passed explicitly or propagated automatically. with a targeting keyA unique identifier used to target specific users or entities when evaluating feature flags. It helps determine which variation of a flag should be served based on predefined rules and conditions. to evaluate flags. The evaluation context passes targeting information such as user IDs, email addresses, or plan types for flag targeting.

For example:

let context = ImmutableContext(
    targetingKey: "martin", 
    structure: ImmutableStructure(attributes: [ 
        "email": Value.String(someValue),
        "age": Value.Integer(30)
]))
OpenFeatureAPI.shared.setEvaluationContext(evaluationContext: context)

let client = OpenFeatureAPI.getClient()
let result = client.getBooleanDetails("premium-feature", false, context)

To set a targeting key during initialization:

let initialContext = ImmutableContext(targetingKey = "user-123")
OpenFeatureAPI.setProvider(provider, initialContext = initialContext)

To change a targeting key at runtime:

let newContext = ImmutableContext(targetingKey = "user-456")
OpenFeatureAPI.setEvaluationContext(newContext)

Observe provider events​

The Harness FME OpenFeature provider emits eventsA record of user or system behavior (such as a page visit, button click, or transaction) associated with a unique key and timestamp. Events are not tied to a specific flag; FME's attribution engine links them to flag evaluations after the fact. when provider state changes (for example, when flags update, configuration changes, or errors) occur. You can observe these events to update your application's behavior in real time.

You can enable your application to:

  • Refresh feature-dependent UI when flags change
  • Gracefully handle degraded states (i.e., when the provider becomes stale)
  • Log or alert on configuration or network issues
  • Control initialization flows based on provider readiness

For example:

import Combine

let cancellable = OpenFeatureAPI.shared.observe().sink { event in
    switch event {
    case ProviderEvent.ready:
        // Provider ready
    case ProviderEvent.stale:
        // Provider stale
    case ProviderEvent.configurationChanges:
        // Configuration changed
    case ProviderEvent.contextChanged:
        // Context updated
    case ProviderEvent.error(let errorCode, let message):
        // Handle error
    default:
        break
    }
}

For more information, go to the Harness FME iOS OpenFeature Provider GitHub repository.