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justeat
133 Stars 18 Forks Apache License 2.0 188 Commits 1 Opened issues

Description

JustTweak is a framework for feature flagging and A/B testing for iOS apps.

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JustTweak

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JustTweak is a framework for feature flagging and A/B testing for iOS apps. It provides a simple facade interface interacting with multiple providers that are queried respecting a given priority. Tweaks represent flags used to drive decisions in the client code.

With JustTweak you can achieve the following:

  • use a JSON local configuration providing default values for experimentation
  • use a number of remote configuration providers such as Firebase and Optmizely to run A/B tests and feature flagging
  • enable, disable, and customize features locally at runtime
  • provide a dedicated UI for customization (this comes particularly handy for feature that are under development to showcase it to stakeholders)

Installation

JustTweak is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "JustTweak"

Implementation

Integration

  • define a JSON configuration file including your features (you can use the included
    ExampleConfiguration.json
    as a template)
  • define your features and A/B tests in your services such as Firebase and Optmizely (optional)
  • configure the JustTweak stack as following
static let tweakManager: TweakManager = {
    // mutable configuration (to override tweaks from other configurations)
    let userDefaultsConfiguration = UserDefaultsConfiguration(userDefaults: UserDefaults.standard)

// remote configurations (optional)
let optimizelyConfiguration = OptimizelyConfiguration()
optimizelyConfiguration.userId = 
let firebaseConfiguration = FirebaseConfiguration()

// local JSON configuration (default tweaks)
let jsonFileURL = Bundle.main.url(forResource: "ExampleConfiguration", withExtension: "json")!
let localConfiguration = LocalConfiguration(jsonURL: jsonFileURL)

// priority is defined by the order in the configurations array (from highest to lowest)
let configurations: [Configuration] = [userDefaultsConfiguration,
                                       optimizelyConfiguration,
                                       firebaseConfiguration,
                                       localConfiguration]
return TweakManager(configurations: configurations)

}()

The order of the objects in the

configurations
array defines the priority of the configurations.

The

MutableConfiguration
with the highest priority, such as
UserDefaultsConfiguration
in the example above, will be used to reflect the changes made in the UI (
TweakViewController
). The
LocalConfiguration
should have the lowest priority as it provides the default values from a local configuration and it's the one used by the
TweakViewController
to populate the UI.

Usage

The three main features of JustTweak can be accessed from the

TweakManager
instance to drive code path decisions.
  1. Checking if a feature is enabled
// check for a feature to be enabled
let enabled = tweakManager.isFeatureEnabled("some_feature")
if enabled {
    // enable the feature
} else {
    // default behaviour
}
  1. Get the value of a flag for a given feature.
    TweakManager
    will return the value from the configuration with the highest priority and automatically fallback to the others if no set value is found.

Use either

tweakWith(feature:variable:)
or the provided property wrappers.
// check for a tweak value
let tweak = tweakManager.tweakWith(feature: "some_feature", variable: "some_flag")
if let tweak = tweak {
    // tweak was found in some configuration, use tweak.value
} else {
    // tweak was not found in any configuration
}

@TweakProperty
and
@OptionalTweakProperty
property wrappers are available to mark properties representing feature flags. Mind that by using these property wrappers, a static instance of
TweakManager
is needed.
@TweakProperty(fallbackValue: ,
               feature: ,
               variable: ,
               tweakManager: )
var labelText: String
@OptionalTweakProperty(fallbackValue: ,
                       feature: ,
                       variable: ,
                       tweakManager: )
var meaningOfLife: Int?
  1. Run an A/B test
// check for a tweak value
let variation = tweakManager.activeVariation(for: "some_experiment")
if let variation = variation {
    // act according to the kind of variation (e.g. "control", "variation_1")
} else {
    // default behaviour
}

Caching

The

TweakManager
provides the option to cache the tweak values in order to improve performance. Caching is disabled by default but can be enabled via the
useCache
property. When enabled, there are two ways to reset the cache:
  • call the
    resetCache
    method on the
    TweakManager
  • post a
    TweakConfigurationDidChangeNotification
    notification

Update a configuration at runtime

JustTweak comes with a ViewController that allows the user to edit the

MutableConfiguration
with the highest priority.
func presentTweakViewController() {
    let tweakViewController = TweakViewController(style: .grouped, tweakManager: )

// either present it modally
let tweaksNavigationController =     UINavigationController(rootViewController:tweakViewController)
tweaksNavigationController.navigationBar.prefersLargeTitles = true
present(tweaksNavigationController, animated: true, completion: nil)

// or push it on an existing UINavigationController
navigationController?.pushViewController(tweakViewController, animated: true)

}

When a value is modified in any

MutableConfiguration
, a notification is fired to give the clients the opportunity to react and reflect changes in the UI.
override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.defaultCenter().addObserver(self,
                                                   selector: #selector(updateUI),
                                                   name: TweakConfigurationDidChangeNotification,
                                                   object: nil)
}

@objc func updateUI() { // update the UI accordingly }

Customization

JustTweak comes with three configurations out-of-the-box:

  • UserDefaultsConfiguration
    which is mutable and uses
    UserDefaults
    as a key/value store
  • LocalConfiguration
    which is read-only and uses a JSON configuration file that is meant to be the default configuration
  • EphemeralConfiguration
    which is simply an instance of
    NSMutableDictionary

In addition, JustTweak defines

Configuration
and
MutableConfiguration
protocols you can implement to create your own configurations to fit your needs. In the example project you can find a few example configurations which you can use as a starting point.

License

JustTweak is available under the Apache 2.0 license. See the LICENSE file for more info.

  • Just Eat iOS team

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