UIAlertview Delegate Method not calling in Child View Controller

问题

I have two controllers

VC A -> Parent and VC B -> Child

Alert view delegate method i.e

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.

回答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

回答2:

You are setting AlertView delegate to self, Self means Child, Change delegate to VC A.

alertView.delegate = self.parent?.parent

回答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 (i.e. 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.

来源：https://stackoverflow.com/questions/41670544/uialertview-delegate-method-not-calling-in-child-view-controller