Basic feature flags in Swift

Feature Flag.swift

//: # Feature Flag example

//: ## Implementation

import Foundation

enum Feature: String {
    case Login, AdminTool
    
    var key: String {
        return "FEATURE_FLAG_\(rawValue.uppercased())"
    }
    
    var isEnabled: Bool {
        guard let flag = ProcessInfo().environment[key] else { return false }
        return flag == "on"
    }

    func toggledOn(block: ()->()) {
        if isEnabled {
            block()
        }
    }

    func toggledOff(block: ()->()) {
        if !isEnabled {
            block()
        }
    }
}

//: ## Usage Example

Feature.Login.toggledOn {
    print("do this if feature is on")
}

Feature.Login.toggledOff {
    print("do this if feature is off")
}