Swift 4 and higher

You can use this anywhere to verify that the user is seeing this view for the first time.

func isAppAlreadyLaunchedOnce() -> Bool {
    let defaults = UserDefaults.standard
    if let _ = defaults.string(forKey: "isAppAlreadyLaunchedOnce") {
        print("App already launched")
        return true
    } else {
        defaults.set(true, forKey: "isAppAlreadyLaunchedOnce")
        print("App launched first time")
        return false
    }
}

Note: This method would return false after user re-installs app and launch first time.