如何彈出初始視圖控制器

Question

假設我有兩個視圖控制器，視圖控制器A和視圖控制器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)
    }
}

每當有人單擊callViewControllerBButtonClicked()按鈕時，它將實例化一個新的視圖控制器ViewControllerB並將其呈現在ViewControllerA頂部。 我現在面臨的問題是即使我已經在ViewControllerB上，它仍然運行此功能

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

如何彈出ViewControllerA？

Answer 1

試試這個代碼-

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)
    }
}