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iOS/tvOS/macOS Client SDK

Installation​

To use the SDK in your project, you must add Statsig as a dependency.

In your Xcode, select File > Swift Packages > Add Package Dependency and enter the URL https://github.com/statsig-io/ios-sdk.git.

You can also include it directly in your project's Package.swift. Find out the latest release version on our GitHub page.

//...
dependencies: [
    // see the latest version on https://github.com/statsig-io/ios-sdk/releases
    .package(url: "https://github.com/statsig-io/ios-sdk.git", .upToNextMinor("X.Y.Z")),
],
//...
targets: [
    .target(
        name: "YOUR_TARGET",
        dependencies: ["Statsig"]
    )
],
//...

Initialize the SDK​

After installation, you will need to initialize the SDK using a Client SDK key from the "API Keys" tab on the Statsig console.

These Client SDK Keys are intended to be embedded in client side applications. If need be, you can invalidate or create new SDK Keys for other applications/SDK integrations.

info

Do NOT embed your Server Secret Key in client-side applications, or expose it in any external-facing documents. However, if you accidentally expose it, you can create a new one in the Statsig console.

In addition to the SDK key, you should also pass in a StatsigUser for feature gate targeting and experimentation grouping purposes.

The 3rd parameter is optional and allows you to pass in a [StatsigOptions](#statsig-options) to customize the SDK.
Statsig.start(
    sdkKey: "my_client_sdk_key",
    user: StatsigUser(userID: "my_user_id"),
    options: StatsigOptions(environment: StatsigEnvironment(tier: .Staging)))
{ errorMessage in

  // Statsig has finished fetching the latest feature gate and experiment values for your user.
  // If you need the most recent values, you can get them now.

  // You can also check errorMessage for any debugging information.

}

The completion block is called after the network request to fetch the latest feature gate and experiment values for your user. If you try to get any value before the completion block is called, you could get either the cached value from the previous session, or the default value. If you need the latest value, please wait for the completion block to be called first.

Working with the SDK​

Checking a Feature Flag/Gate​

Now that your SDK is initialized, let's check a Feature Gate. Feature Gates can be used to create logic branches in code that can be rolled out to different users from the Statsig Console. Gates are always CLOSED or OFF (think return false;) by default.

if Statsig.checkGate("new_homepage_design") {
  // Gate is on, show new home page
} else {
  // Gate is off, show old home page
}

Reading a Dynamic Config​

Feature Gates can be very useful for simple on/off switches, with optional but advanced user targeting. However, if you want to be able send a different set of values (strings, numbers, and etc.) to your clients based on specific user attributes, e.g. country, Dynamic Configs can help you with that. The API is very similar to Feature Gates, but you get an entire json object you can configure on the server and you can fetch typed parameters from it. For example:

let config = Statsig.getConfig("awesome_product_details")

// The 2nd parameter is the default value to be used in case the given parameter name does not exist on
// the Dynamic Config object. This can happen when there is a typo, or when the user is offline and the
// value has not been cached on the client.
let itemName = config.getValue(forKey: "product_name", defaultValue: "Awesome Product v1")
let price = config.getValue(forKey: "price", defaultValue: 10.0)
let shouldDiscount = config.getValue(forKey: "discount", defaultValue: false)

Getting an Layer/Experiment​

Then we have Layers/Experiments, which you can use to run A/B/n experiments. We offer two APIs, but we recommend the use of layers to enable quicker iterations with parameter reuse.

// Values via getLayer

let layer = Statsig.getLayer("user_promo_experiments")
let promoTitle = layer.getValue(forKey: "title", defaultValue: "Welcome to Statsig!")
let discount = layer.getValue(forKey: "discount", defaultValue: 0.1)

// or, via getExperiment

let titleExperiment = Statsig.getExperiment("new_user_promo_title")
let priceExperiment = Statsig.getExperiment("new_user_promo_price")

let promoTitle = titleExperiment.getValue(forKey: "title", defaultValue: "Welcome to Statsig")
let discount = priceExperiment.getValue(forKey: "discount", defaultValue: 0.1)

...

let price = msrp * (1 - discount);

Logging an Event​

Now that you have a Feature Gate or an Experiment set up, you may want to track some custom events and see how your new features or different experiment groups affect these events. This is super easy with Statsig - simply call the Log Event API for the event, and you can additionally provide some value and/or an object of metadata to be logged together with the event:

Statsig.logEvent(withName: "purchase", value: 2.99, metadata: ["item_name": "remove_ads"])

Learn more about identifying users, group analytics, and best practices for logging events in the logging events guide.

Parameter Stores​

Parameter Stores hold a set of parameters for your mobile app. These parameters can be remapped between Statsig entities (Feature Gates, Experiments, and Layers), so you can decouple your code from the configuration in Statsig.

You can read more about the concept here.

Getting a Parameter Store​

To fetch a set of parameters, use the following api:

val homepageStore = Statsig.getParameterStore("homepage")

Getting a parameter​

You can then access parameters like this:

let title = homepageStore.getValue(forKey: "title", defaultValue: "Welcome")

let shouldShowUpsell = homepageStore.getValue(forKey: "upsell_upgrade_now", defaultValue: false)

Statsig User​

You should provide a StatsigUser object whenever possible when initializing the SDK, passing as much information as possible in order to take advantage of advanced gate and config conditions (like country or OS/browser level checks).

Most of the time, the userID field is needed in order to provide a consistent experience for a given user (see logged-out experiments to understand how to correctly run experiments for logged-out users).

If the user is logged out at the SDK init time, you can leave the `userID` out for now, and we will use a stable device ID that we create and store in the local storage for targeting purposes.

Besides userID, we also have email, ip, userAgent, country, locale and appVersion as top-level fields on StatsigUser. In addition, you can pass any key-value pairs in an object/dictionary to the custom field and be able to create targeting based on them.

Once the user logs in or has an update/changed, make sure to call `updateUser` with the updated `userID` and/or any other updated user attributes:
let newUser = StatsigUser(userID: "new_user_id", email: "newUser@gmail.com", country: "US")

Statsig.updateUser(newUser) { errorMessage in

  // Statsig has finished fetching the latest feature gate and experiment values for your updated user.
  // If you need the most recent values, you can get them now.

}

Private Attributes​

Have sensitive user PII data that should not be logged? No problem, we have a solution for it! On the StatsigUser object we also have a field called privateAttributes, which is a simple object/dictionary that you can use to set private user attributes. Any attribute set in privateAttributes will only be used for evaluation/targeting, and removed from any logs before they are sent to Statsig server.

For example, if you have feature gates that should only pass for users with emails ending in "@statsig.com", but do not want to log your users' email addresses to Statsig, you can simply add the key-value pair { email: "my_user@statsig.com" } to privateAttributes on the user and that's it!

Statsig Options​

Statsig.start() takes an optional parameter options in addition to sdkKey and user that you can provide to customize the Statsig client. Here are the current options and we are always adding more to the list:

  • initTimeout: Double, default 3.0

    • used to decide how long the Statsig client waits for the initial network request to respond before calling the completion block. The Statsig client will return either cached values (if any) or default values if checkGate/getConfig/getExperiment is called before the initial network request completes.
    • If you always want to wait for the latest values fetched from Statsig server, you should set this to 0 so we do not timeout the network request.

  • disableCurrentVCLogging: Bool, default false

    • by default, any custom event your application logs with Statsig.logEvent() includes the current root View Controller. This is so we can generate user journey funnels for your users. You can set this parameter to true to disable this behavior.

  • environment: StatsigEnvironment, default nil

    • StatsigEnvironment is a class for you to set environment variables that apply to all of your users in the same session and will be used for targeting purposes.
    • e.g. passing in a value of StatsigEnvironment(tier: .Staging) will allow your users to pass any condition that pass for the staging environment tier, and fail any condition that only passes for other environment tiers.

  • evaluationCallback: EvaluationCallbackData, default nil

    • EvaluationCallback provides a callback when an evaluation is made against one of your configurations (gate, dynamic config, experiment, layer and parameter stores). This is useful when you want to trigger specific actions or log evaluations based on the results received from Statsig.
    • To use the EvaluationCallback, you need to provide a callback function during the SDK initialization via the StatsigOptions. The callback is invoked every time an evaluation occurs for feature gates, dynamic configs, experiments, layers, or parameter stores.
    • The EvaluationCallbackData enum defines the different types of data that can be returned in the evaluationCallback when the Statsig iOS SDK evaluates feature gates, dynamic configs, experiments, layers, or parameter stores.

    Here is the structure of the enum:

       public enum EvaluationCallbackData {
          case gate (FeatureGate)
          case config (DynamicConfig)
          case experiment (DynamicConfig)
          case layer (Layer)
          case parameterStore (ParameterStore)
       }

    Here's an example of how to set up an evaluation callback:

        func callback(data: StatsigOptions.EvaluationCallbackData) {
           switch data {
           case .gate(let gate):
              // Handle gate evaluation
           case .config(let config):
              // Handle dynamic config evaluation
           case .experiment(let experiment):
              // Handle experiment evaluation
           case .layer(let layer):
              // Handle layer evaluation
           case .parameterStore(let paramStore):
              // Handle parameter store evaluation
           }
        }

        let opts = StatsigOptions(evaluationCallback: callback)
        Statsig.start(sdkKey: "client-key", options: opts)

  • storageProvider: StorageProvider, default nil

    • Allows users to implement their own caching strategy by passing an object that conforms to the StorageProvider protocol.

    • Default cache key: com.statsig.cache

       @objc public protocol StorageProvider {
          @objc func read(_ key: String) -> Data?
          @objc func write(_ value: Data, _ key: String)
          @objc func remove(_ key: String)
       }

  • overrideStableID: String, default nil

    • Overrides the auto generated StableID that is set for the device.

  • enableCacheByFile: Bool, default false

    • Use file caching instead of UserDefaults. Useful if you are running into size limits with UserDefaults (ie tvOS).

  • initializeValues: [String: Any], default nil

    • Provide a Dictionary representing the "initialize response" required to synchronously initialize the SDK. This value can be obtained from a Statsig server SDK.

  • disableDiagnostics: Bool, default false

    • Prevent the SDK from sending useful debug information to Statsig.

  • disableHashing: Bool, default false

    • When disabled, the SDK will not hash gate/config/experiment names, instead they will be readable as plain text.
    • Note: This requires special authorization from Statsig. Reach out to us if you are interested in this feature.

  • shutdownOnBackground: Bool, default true

    • The SDK automatically shuts down when an app is put into the background. If you need to use the SDK while your app is in the background, set this to false.

Shutting Statsig Down​

In order to save users' data and battery usage, as well as prevent logged events from being dropped, we keep event logs in client cache and flush periodically. Because of this, some events may not have been sent when your app shuts down.

To make sure all logged events are properly flushed or saved locally, you should tell Statsig to shutdown when your app is closing:

Statsig.shutdown()

Local Overrides​

If you want to locally override gates/configs/experiments/layers, there are a set of override APIs as follows.

// Overrides the given gate to the specified value
Statsig.overrideGate("a_gate_name", value: true)

// Overrides the given config (dynamic config or experiment) to the provided value
Statsig.overrideConfig("a_config_or_experiment_name", value: ["key": "value"])

// Overrides the given layer to the provided value
Statsig.overrideLayer("a_layer_name", value: ["key": "value"])

// Removes any overrides associated with the provided gate/config/experiment/layer name
Statsig.removeOverride("a_gate_name")
Statsig.removeOverride("a_config_or_experiment_name")
Statsig.removeOverride("a_layer_name")

// Removes all overrides
Statsig.removeAllOverrides()

// Returns a StatsigOverrides object, contain all the current overrides
let currentOverrides = Statsig.getAllOverrides()
note
  1. These only apply locally on the device where they are being tested - they do not update definitions in the Statsig console or elsewhere.
  2. These will be persisted to local storage on the device, so overrides will persist across sessions. If you want to clear out the overrides, you can remove them all with removeAllOverrides or remove a specific override with removeOverride
  3. The local override API is not designed to be a full mock. They are only a convenient way to override the value of the gate/config/etc.

Manual Exposures v1.16.0+​

warning

Manually logging exposures can be tricky and may lead to an imbalance in exposure events. For example, only triggering exposures for users in the Test group of an experiment will imbalance the experiment, making it useless.

Added in version 1.16.0, you can now query your gates/experiments without triggering an exposure as well as manually logging your exposures.

To check a gate without an exposure being logged, call the following.

// Swift
let result = Statsig.checkGateWithExposureLoggingDisabled("a_gate_name")
	
// Objective C
bool result = [Statsig checkGateWithExposureLoggingDisabled:@"a_gate_name"];

Later, if you would like to expose this gate, you can call the following.

// Swift
Statsig.manuallyLogGateExposure("a_gate_name")
	
// Objective C
[Statsig manuallyLogGateExposure:@"a_gate_name"];

stableID​

Each client SDK has the notion of stableID, and identifier that is generated the first time the SDK is initialized and is stored locally for all future sessions. Unless storage is wiped (or app deleted), the stableID will not change. This allows us to run device level experiments and experiments when other user identifiable information is unavailable (Logged out users).

You can get the stableID for the current device with:

Statsig.getStableID();

If you have your own form of stableID and would prefer to use it instead of the Statsig generated ID, you can override it through StatsigOptions:

let opts = StatsigOptions(overrideStableID: "my_stable_id")
Statsig.start(sdkKey: "client-xyx", options: opts)

StatsigListening v1.14.0+​

In version v1.14.0+, you can now listen for changes in Statsig values.

This can be useful if you have one location that calls Statsig.start or Statsig.updateUser and you would like these changes to flow to separate locations.

To use this API, simply have the class you wish to respond to these changes implement the StatsigListening protocol and add it as a listener.

The StatsigListening protocol has two methods that can be implemented:

onInitialized - Will be called when the initialize request is returned in Statsig.start(). An error string may be passed to this function if something went wrong with the network request.

onUserUpdated - Will be called when the network request for Statsig.updateUser is returned. An error string may be passed to this function if something went wrong with the network request.

You may also check the new Statsig.isInitialized() to verify if Statsig has already completed initialization.

The following is an example of how this could be done in a ViewController

class MyViewController: UIViewController, StatsigListening {

    override func viewDidLoad() {
        super.viewDidLoad()

        if Statsig.isInitialized() {
            render()
        } else {
            Statsig.addListener(self)
            renderLoading()
        }
    }

    private func render() {
        var showNewUI = Statsig.checkGate("new_ui_enabled", false)
        if showNewUI {
            // Render the new
        } else {
            // Render the old
        }
    }

    private func renderLoading() { /* Some Loading UI */ }

    private func renderError(error: String) { /* Some Error UI */ }

    // StatsigListening Implementation

    func onInitialized(_ error: String?) {
        if (error) {
            renderError(error)
        }
        render()
    }

    func onUserUpdated(_ error: String?) { /* Optional rerender when User changed */ }
}

Using multiple instances of the SDK​

Our documentation up to this point guides you through setting up your Statsig integration via the singleton Statsig.

There are cases where you may need to create multiple instances of the Statsig SDK. Each SDK supports this as well - the Statsig singleton wraps a single instance of the SDK (typically called a StatsigClient) that you can instantiate.

🔥IMPORTANT: You must use a different SDK key for each sdk instance you create for this to work. Various functionality of the Statsig client is keyed on the SDK key being used. Using the same key will lead to collisions.

All top level static methods from the singleton carry over as instance methods. To create an instance of the Statsig sdk:

var client = StatsigClient(sdkKey: sdkKey, user: user, options: options, completion: completion)

FAQ​

How do I run experiments for logged out users?​

See the guide on device level experiments

Does the SDK support tvOS?​

v1.13.1+ of the statsig ios SDK will supports tvOS