FeatureFlagsController

FeatureFlagsController is a micro-library to automatically build a SwiftUI Form View from all registered feature flags in a project, leveraging power of functional reactive programming using Combine.

Requirements

• iOS 13.0+
• Xcode 13.0+
• Swift 5.5+

Installation

CocoaPods

Add the following to your Podfile:

pod "FeatureFlagsController"

Swift Package Manager

https://github.com/DataDog/FeatureFlagsController using Xcode 12 SPM integration

Usage

FeatureFlagsView

All registered feature flags appear in a FeatureFlagsView which is a SwiftUI.View composed of a NavigationView and a sectioned Form. You can display this view anywhere in your application. In a hidden “debug” menu for example.

This form keeps track of registered feature flags and display the right UI to modify them at runtime. A ToggleFeatureFlag will display a simple Toggle (UISwitch) while a PickerFeatureFlag will display a segmented control or a sub-menu depending the picker style it is given.

Declaration

Here is how you declare a new Feature Flag:

let roundedCornersFeatureFlag = ToggleFeatureFlag(
    title: "Rounded Corners", defaultValue: true, group: "Home Screen"
)

Declaring a feature flag doesn’t do anything on its own, but you still can access its value using the value property. Some feature flags types have an alias to the value property to make the call-site more clear. For example, the ToggleFeatureFlag has the isEnabled alias.

Registration

In order to display a feature flag in the FeatureFlagsView, a feature flag must be registered. The register() methods return a Combine AnyPublisher<Value, Never> emitting immediately the current value, then all value updates.

Once the Combine subscription is cancelled (for example, when the owning view controller is popped or dismissed), the feature flag disappears from the FeatureFlagsView.

roundedCornersFeatureFlag
    .register() // Adds the feature flag to the `FeatureFlagsView` and returns an AnyPublisher<Bool, Never>
    .map { $0 ? 16 : 0 } // Use all Combine operators you want to
    .assign(to: \.cornerRadius, on: squareView.layer) 
    .store(in: &cancellables) // On cancellation, the feature flag is removed from the `FeatureFlagsView`

SwiftUI

In SwiftUI, it’s even simpler. You can just use the @FeatureFlag property wrapper, either by passing a declared feature flag, or by using a convenience init.

static let roundedCornersFeatureFlag = ToggleFeatureFlag(
    title: "Rounded Corners", defaultValue: true, group: "Home Screen"
)

@FeatureFlag(Self.roundedCornersFeatureFlag) var hasRoundedCorners

Or…

@FeatureFlag(title: "Rounded Corners", group: "Home Screen") 
var hasRoundedCorners = true

You can also use the projected value to get the underlying feature flag:

Text($hasRoundedCorners.title)

License

This framework is provided under the MIT license.