Swift 3.0委托協議不起作用

Question

我已經在兩個視圖控制器中創建了委托協議。 但委托方法不會調用我的代碼段。 這是什么原因。 我找不到問題，請發表您的建議以重溫此問題。

主視圖控制器

class ViewController: UIViewController, testDelegateMethod {

override func viewDidLoad() {
    super.viewDidLoad()

    let vw = testViewController()
    vw.delegateTest = self

    let push = self.storyboard?.instantiateViewController(withIdentifier: "testViewController")
    self.navigationController?.pushViewController(push!, animated: true)
}

func testMethod(value:String) {
    print("Hai", value)
}
}

子視圖控制器

protocol testDelegateMethod {
func testMethod(value:String)
}

class testViewController: UIViewController {
var delegateTest : testDelegateMethod?

override func viewDidLoad() {
    super.viewDidLoad()
}

@IBAction func actSubmit(_ sender: Any) {
    delegateTest?.testMethod(value: "Hello how are you!")
}

}

Answer 1

由於此行，您面臨的問題

let vw = testViewController()
    vw.delegateTest = self

您已經創建了testViewController vw的實例，並已分配了vw實例的委托

在下一行

let push = self.storyboard?.instantiateViewController(withIdentifier: "testViewController")
self.navigationController?.pushViewController(push!, animated: true)

您正在創建不同的testviewcontroller push實例

不需要此代碼，

let vw = testViewController()
        vw.delegateTest = self

相反做

let push testViewController = self.storyboard.instantiateViewController(withIdentifier: "testViewController") as! testViewController
push.delegateTest = self
self.navigationController?.pushViewController(push, animated: true)

Answer 2

在viewdidLoad()方法中更新這些更改

override func viewDidLoad() {
    super.viewDidLoad()

   if let push = self.storyboard?.instantiateViewController(withIdentifier: "testViewController") as? SelectionScreen
  {
    push.delegateTest = self
  }

}

Answer 3

let vw = testViewController() // Your are doing wrong code 
vw.delegateTest = self   

僅使用此

我希望它對你有用

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let push = storyboard.instantiateViewController(withIdentifier:"testViewController")as! testViewController
push.delegateTest = self
self.navigationController?.pushViewController(push, animated: true)

Answer 4

此代碼段沒有意義。 您只是創建一個對象，而不再使用它。 因此，請刪除此代碼段。

  let vw = testViewController()
        vw.delegateTest = self

並這樣做：

override func viewDidLoad() {
    super.viewDidLoad()
    let pushVC = self.storyboard?.instantiateViewController(withIdentifier: "testViewController") as! testViewController
 pushVC.delegateTest = self

    self.navigationController?.pushViewController(pushVC, animated: true)
}

Answer 5

我認為，您將代碼func testMethod(value:String) { print("Hai", value) }放入viewDidLoad中，然后let push = self.storyboard?.instantiateViewController(withIdentifier: "testViewController") self.navigationController?.pushViewController(push!, animated: true)