我在第一个 View Controller ViewController 中有一个标签,并且在第二个 vc 中有一个获取日期的函数。我想在第二个定时器启动后更新第一个标签。使用协议(protocol)委托(delegate)模式好吗?此时它不起作用,时间在流逝,但没有更新第一个 VC 中的 View
我的协议(protocol)结构
protocol ViewControllerDelegate: class {
func changeLabelText(textToPass: String)
}
在第一个 View Controller 中
class ViewController: UIViewController, ViewControllerDelegate {
@IBOutlet weak var mainLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
func changeLabelText(textToPass: String) {
self.mainLabel.text = textToPass
self.view.layoutIfNeeded()
}
@IBAction func buttonTapped(_ sender: UIButton) {
let nextVC = storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
nextVC.delegateSubscriber = self
present(nextVC, animated: true, completion: nil)
}
}
在第二个VC中
class SecondViewController: UIViewController {
//MARK: speed timer feature 1/3
private weak var timer: Timer?
private var timerDispatchSourceTimer : DispatchSourceTimer?
weak var delegateSubscriber : ViewControllerDelegate?
@IBOutlet weak var myTxtField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
startTimer(every: 1)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
print("appeared")
stopTimer()
}
private func startTimer(every timeInterval: TimeInterval) {
if #available(iOS 10.0, *) {
timer = Timer.scheduledTimer(withTimeInterval: timeInterval, repeats: true) { [weak self] _ in
let dateToPass = Date().description
print(dateToPass)
self?.delegateSubscriber?.changeLabelText(textToPass: dateToPass)
}
}
}
//MARK: speed timer feature 3/3
private func stopTimer() {
timer?.invalidate()
//timerDispatchSourceTimer?.suspend() // if you want to suspend timer
timerDispatchSourceTimer?.cancel()
}
@IBAction func buttonTapped(_ sender: UIButton) {
// delegateSubscriber?.changeLabelText(textToPass: self.myTxtField.text ?? "error")
dismiss(animated: true, completion: nil)
}
}
最佳答案
只需从 Timer
闭包中删除 [weak self]
timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { _ in
let dateToPass = Date().description
print(dateToPass)
self.delegateSubscriber?.changeLabelText(textToPass: dateToPass)
}
...那么 self
不是可选的
关于swift 如何从第二个 vai 协议(protocol)和委托(delegate)模式中的逻辑更新第一个 Controller ?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53792680/