how to detect first launch

In every app it’s very good to know if the user launch it first time or not. This code can solve the problem.

let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
if launchedBefore  {
    print("Not first launch.")
} else {
    print("First launch, setting UserDefault.")
    UserDefaults.standard.set(true, forKey: "launchedBefore")
}

let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")

if launchedBefore {

print("Not first launch.")

} else {

print("First launch, setting UserDefault.")

UserDefaults.standard.set(true, forKey: "launchedBefore")

}

O.. in ViewDidLoad{}