UIAlertview Delegate Method not calling in Child View Controller

Question

I have two controllers

VC A -> Parent and VC B -> Child

Alert view delegate method ie

func alertView(View: UIAlertView!, clickedButtonAtIndex buttonIndex: Int){}

is declared in VC A .

When i display alert from VC B delegate method is not called on alert button clicked.

Answer 1

protocol alertViewDelegate:class {
    func alertView(View: UIAlertView!, clickedButtonAtIndex buttonIndex: Int)
}

Create an alert view delegate object in parent class VC A

weak var delegate:alertViewDelegate() ?= nil

Implement the delegate in VC B and Set the delegate object in VC B

let alertview = alertView()
alertview.delegate  = self

Answer 2

您将AlertView委托设置为 self，Self 表示Child ，将委托更改为 VC A。

alertView.delegate = self.parent?.parent

Answer 3

Follow these step by step:

1. Create a protocol in your VC-B as:

    protocol AlertViewProtocol:class { func alertView(View: UIAlertView!, clickedButtonAtIndex buttonIndex: Int) }

2. Add a var in your VC-B class as:

    var delegate: AlertViewProtocol?

3. Use the delegate in any class method of VC-B to send the data to the receiving method (ie any method of VC-A), which is any method that adopts the protocol. Follow this pattern to use the delegate:

    delegate?.alertView(View: UIAlertView!, clickedButtonAtIndex buttonIndex: Int) // Above statement is like a method calling (on delegate var), use your parameters accordingly

4. Adopt the protocol in your recieving class (here, VC-A):

    class ViewControllerA: UIViewController, AlertViewProtocol { ... ... }

5. Implement the delegate method in VC-A:

    func alertView(View: UIAlertView!, clickedButtonAtIndex buttonIndex: Int) { // Do your stuff // when you click on the designated button in your VC-B, this method will be invoked }

6. Set the delegate in VC-A where you are instantiating the VC-B object. In my case this is like:

Here, vcb?.delegate = self is very important. If you forget to set the delegate property of the object with self the delegation process won't work.

    @IBAction func showVCB(sender: AnyObject) {
        let vcb: ViewControllerB? = self.storyboard?.instantiateViewControllerWithIdentifier("viewcontrollerB") as? ViewControllerB
        vcb?.delegate = self
        self.presentViewController(vcb!, animated: true, completion: nil)
    }

Hope, this helps you for understanding the process of how the delegates work.