//TODO: Add it in appDelegate > didFinishLaunchingWithOptions
extension UIApplication {
    class func isFirstLaunch() -> Bool {
        if !NSUserDefaults.standardUserDefaults().boolForKey("HasAtLeastLaunchedOnce") {
            NSUserDefaults.standardUserDefaults().setBool(true, forKey: "HasAtLeastLaunchedOnce")
            NSUserDefaults.standardUserDefaults().synchronize()
            return true
        }
        return false
    }
}

//TODO: Call it inside appDelegate before calling any other view controller
if UIApplication.isFirstLaunch() {
    // do something on first launch
}