ios - 如何弹出初始 View Controller

Question

假设我有两个 View Controller ， View Controller A 和 View Controller B

class ViewControllerA: UIViewController {
     override func viewDidLoad() {
        super.viewDidLoad()
        // it runs this function every 5 seconds
         Timer.scheduledTimer(5, target: self,selector: #selector(ViewControllerA.printNumber), userInfo: nil, repeats: true)
    }

    @IBAction func callViewControllerBButtonClicked(_ sender: UIButton) {
         if let vc = self.storyboard?.instantiateViewController(withIdentifier: "ViewControllerBID") as? ViewControllerB {

                self.present(vc, animated: true, completion: nil)
        }

    }

    func printNumber() {
      print(0)
    }
}

每当有人点击callViewControllerBButtonClicked()按钮时，它就会实例化一个新的 View Controller ，即ViewControllerB，并将其呈现在ViewControllerA之上。我现在面临的问题是，即使我已经在 ViewControllerB 上，它仍然运行这个函数

Timer.scheduledTimer(5, target: self,selector: #selector(ViewControllerA.printNumber), userInfo: nil, repeats: true)

如何弹出 ViewControllerA？

Answer 1

试试这个代码 -

class ViewControllerA: UIViewController {
     var timer : Timer!
     override func viewDidLoad() {
        super.viewDidLoad()
        // it runs this function every 5 seconds
        timer = Timer.scheduledTimer(5, target: self,selector: #selector(ViewControllerA.printNumber), userInfo: nil, repeats: true)
    }

    @IBAction func callViewControllerBButtonClicked(_ sender: UIButton) {
         if let vc = self.storyboard?.instantiateViewController(withIdentifier: "ViewControllerBID") as? ViewControllerB {
            timer.invalidate()
            self.present(vc, animated: true, completion: nil)
        }

    }

    func printNumber() {
      print(0)
    }
}