func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

    if iDontMindSingletons {
        VersionsTracker.initialize(trackAppVersion: true, trackOSVersion: true)
    }
    else {
        // make sure to update the version history once once during you app's life time
        VersionsTracker.updateVersionHistories(trackAppVersion: true, trackOSVersion: true)
    }

    return true
}

let versionsTracker = iDontMindSingletons ? VersionsTracker.sharedInstance : VersionsTracker()

let curAppVersion : Version = versionsTracker.appVersion.currentVersion
print("Current marketing version is \(curAppVersion.versionString) (Build \(curAppVersion.buildString)) and was first launched \(curAppVersion.installDate)")

let versionsTracker = iDontMindSingletons ? VersionsTracker.sharedInstance : VersionsTracker()

let appVersions: [Version] = versionsTracker.appVersion.versionHistory
let firstOSVerion : Version = versionsTracker.osVersion.versionHistory.first!
print("The very first time the app was launched on iOS \(firstOSVerion.versionString) on \(firstOSVerion.installDate)")

let versionsTracker = iDontMindSingletons ? VersionsTracker.sharedInstance : VersionsTracker()

switch versionsTracker.appVersion.changeState {
case .installed:
    // 🎉 Sweet, a new user just installed your app
    // ... start tutorial / intro
    print("🆕 Congratulations, the app is launched for the very first time")

case .notChanged:
    // 😴 nothing as changed
    // ... nothing to do
    print("🔄 Welcome back, nothing as changed since the last time")

case .updated(let previousVersion: Version):
    // 🙃 new build of the same version
    // ... hopefully it fixed those bugs the QA guy reported
    print("🆙 The app was updated making small changes: \(previousVersion) -> \(versionTracker.currentVersion)")

case .upgraded(let previousVersion):
    // 😄 marketing version increased
    // ... migrate old app data
    print("⬆️ Cool, its a new version: \(previousVersion) -> \(versionTracker.currentVersion)")

case .downgraded(let previousVersion):
    // 😵 marketing version decreased (hopefully we are not on production)
    // ... purge app data and start over
    print("⬇️ Oohu, looks like something is wrong with the current version to make you come back here: \(previousVersion) -> \(versionTracker.currentVersion)")
}    

let versionsTracker = iDontMindSingletons ? VersionsTracker.sharedInstance : VersionsTracker()
let curAppVersion : Version = versionsTracker.appVersion.currentVersion

curAppVersion >= Version("1.2.3")
curAppVersion >= "1.2.3"
Version("1.2.3") < Version("3.2.1")
curAppVersion != Version("1.2.3", buildString: "B19")