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iOS SDK reference

Read time: 3 minutes
Last edited: May 20, 2022


This topic documents how to get started with the iOS SDK, and links to reference information on all of the supported features.

SDK quick links

LaunchDarkly's SDKs are open source. In addition to this reference guide, we provide source, API reference documentation, and sample applications:

SDK API documentationSDK API docs
GitHub repositoryios-client-sdk
Sample applicationshello-ios (Objective-C)
hello-ios-swift (Swift)
hello-macos (macOS)
hello-tvos (tvOS)
Published moduleCocoaPods
SDK version compatibility

The LaunchDarkly iOS SDK, version 4.0.0 and higher, is compatible with applications written in either Swift or Objective-C. The inline code samples include both languages. The SDK is written in Swift.

Getting started

After you complete the Getting started process, follow these instructions to start using the LaunchDarkly SDK in your application.

Including the SDK as a dependency

The first step is to install the LaunchDarkly SDK as a dependency in your application.

LaunchDarkly supports multiple methods for installing the SDK:

  • Using the Swift Package Manager
  • Using CocoaPods
  • Using Carthage
  • Installing the SDK manually

Each method is explained below.

Using the Swift Package Manager

If you use the Swift Package Manager, you can install the SDK through Xcode or include it as a dependency in your Package.swift file.

To add a package dependency to your Xcode project, select File > Swift Packages > Add Package Dependency and enter the iOS SDK repository URL clone URL, then select your desired version constraints.

Including the SDK as a dependency in a Package.swift file looks like this:

dependencies: [
.package(url: "https://github.com/launchdarkly/ios-client-sdk.git", .upToNextMinor("6.1.0")),
targets: [
name: "YOUR_TARGET",
dependencies: ["LaunchDarkly"]

Using CocoaPods

If you use CocoaPods, you can install the SDK by adding the following to your Podfile. To identify the latest version, read the SDK releases page.

Here is the code to add to your Podfile:

target 'YourTargetName' do
pod 'LaunchDarkly', '~> 6.1'

Using Carthage

If you use Carthage, you can install the SDK by specifying it in your Cartfile. To identify the latest version, read the SDK releases page.

Here is the code to include in your Cartfile:

github "launchdarkly/ios-client" ~> 6.1

Installing the SDK manually

For instructions on installing the SDK without CocoaPods or Carthage, read the SDK readme.

Using the SDK in your application

This is a brief overview of using the SDK. Read the detailed sections below for more information on configuration and advanced features.


First import the LaunchDarkly client in your application code:

import LaunchDarkly

Initializing the SDK

After importing the SDK, configure and initialize it. Specify your mobile key when configuring the SDK so that your application is authorized to connect to a particular environment within LaunchDarkly. Your mobile key is available in the Projects tab of your Account settings page. Mobile keys are not secret and you can expose them in your client-side code without risk. Never embed a server-side SDK key into a client-side application.

Here is how to specify your mobile key:

// If you would like the completion to be called even in cases where
// the SDK is unable to retrieve flags for the user, there is a variant
// to the start method that takes a maximum time to wait for flag values.
// This variant notifies the completion whether the operation timed out.
let config = LDConfig(mobileKey: "YOUR_MOBILE_KEY")
let user = LDUser(key: "test-user")
LDClient.start(config: config, user: user, startWaitSeconds: 5) { timedOut in
if timedOut {
// The SDK may not have the most recent flags for the configured user
} else {
// The SDK has received flags for the configured user

However, calling blocking code from the main thread in a mobile app is not considered a best practice. The preferred method is loading the client asynchronously.

Here's how:

let config = LDConfig(mobileKey: "YOUR_MOBILE_KEY")
let user = LDUser(key: "test-user")
LDClient.start(config: config, user: user)
// If you need to ensure that the most recent flags have been received
// start supports an optional completion that is triggered when the SDK
// has retrieved flags for the configured user.
LDClient.start(config: config, user: user) {
// Client has received flags for the user
LDClient must be a singleton

It's important to make LDClient a singleton. The client instance maintains internal state that allows LaunchDarkly to serve feature flags without making any remote requests. Do not instantiate a new client with every request.

Retrieving the client instance

After calling start, you can retrieve the LDClient instance with the static method LDClient.get():

let client = LDClient.get()!

Getting the variation to serve the configured user

Making feature flags available to this SDK

You must make feature flags available to mobile SDKs before the SDK can evaluate those flags. If an SDK tries to evaluate a feature flag that is not available, the user will receive the default value for that flag.

To make a flag available to this SDK, check the SDKs using Mobile key checkbox during flag creation, or on the flag's Settings tab. To make all of a project's flags available to this SDK by default, check the SDKs using Mobile key checkbox in your project Settings.

You can use client to check which variation a particular user will receive for a given feature flag.

Here's how:

let showFeature = client.boolVariation(forKey: "flag-key", defaultValue: false)
if showFeature {
// Application code to show the feature
else {
// The code to run if the feature is off

Background fetch

When the app is backgrounded, the SDK does not receive real-time events. However, MacOS supports background fetch which updates flag values opportunistically, according to iOS standard defaults. iOS does not support background fetch.

To change the background fetch interval for flags in your app, add the following code in your LDConfig:

var ldConfig = LDConfig(mobileKey: "MY_MOBILE_KEY")
ldConfig.backgroundFlagPollingInterval = 3600

Shutting down

Shut down the client when your application terminates. To learn more, read Shutting down.

Data collection

To learn more about data collection within this SDK and implications on submissions to the Apple App Store, read the Apple App Store data collection policy.

Supported features

This SDK supports the following features: