swift should timer be used on main thread code example

Example 1: swift + time delay call main thread

DispatchQueue.main.asyncAfter(deadline: .now() + 1) { 
   //Your code
}

Example 2: use timer swift

Timer.scheduledTimer(timeInterval: 1, 
    target: self, 
    selector: #selector(YourController.update), 
    userInfo: nil, 
    repeats: true)

// @objc selector expected for Timer
@objc func update() {
    // do what should happen when timer triggers an event
}