Flipper

Flipper is a very simple Swift library for feature flipping. Feature flipping is the method of dynamically enabling/disabling pieces of code in your app depending on an availability level. For example, it can be used for enabling beta-only features for beta testers from the same code base as is being shipped to the App Store. No need to maintain multiple branches. It also allows for other use cases such as remote or partial enabling/disabling of features.

First, you need to configure your flipper with various features and their respective enablement level:

let flipper = Flipper()
flipper.addFeature("my_released_feature", level: .Release)
flipper.addFeature("my_beta_feature", level: .Beta)
flipper.addFeature("my_developing_feature", level: .Development)

// or...

let flipper = Flipper([
  "my_released_feature": .Release,
  "my_beta_feature": .Beta,
  "my_developing_feature": .Development,
])

You can then check if a feature is enabled for a certain level. The key point here is that each level includes features enabled for levels "above". So if a feature is enabled for "Beta", it will also be enabled for "Development", as "Beta" is a higher feature level. For example:

flipper.isEnabled("my_beta_feature", level: .Release)     // => false
flipper.isEnabled("my_beta_feature", level: .Beta)        // => true
flipper.isEnabled("my_beta_feature", level: .Development) // => true

You can force also forcefully enable/disable a feature:

flipper.isEnabled("my_beta_feature", level: .Release) // => false

// Force enable
flipper.flipOn("my_beta_feature")
flipper.isEnabled("my_beta_feature", level: .Release) // => true

// Force disable
flipper.flipOff("my_beta_feature")
flipper.isEnabled("my_beta_feature", level: .Beta)    // => false

// Reset to get back to normal
flipper.resetFeature("my_beta_feature")
flipper.isEnabled("my_beta_feature", level: .Beta)   // => true

If you omit the level from the isEnabled() call, the flipper will compare against it's internally configured level as defined by the currentLevel property.

let flipper = Flipper([ "my_beta_feature": .Beta ])

flipper.currentLevel = .Release
flipper.isEnabled("my_beta_feature") // => false

flipper.currentLevel = .Beta
flipper.isEnabled("my_beta_feature") // => true

Finally, for convenience, there is a singleton instance of Flipper available through the read-only sharedFlipper class property. This is useful if you only ever want to use a shared instance throughout your app.