calling a parent UIViewController method from a child UIViewController

Question

I have a Parent UIViewController, which opens a child UIViewController:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("myChildView") as! UIViewController
self.presentViewController(vc, animated: true, completion: nil)

I press a Button in the ChildView which should close the the ChildView and call a method in the Parent View:

self.dismissViewControllerAnimated(true, completion: nil)
CALL PARENTS METHOD  ??????

How to do that ? I found a good answer (Link to good answer), but I am not sure if this is the best practice with UIViewControllers. Can someone help ?

The delegation pattern in your link is the correct way to do it, and it works just fine when you use ViewControllers. The only time it doesn't work is when you're using Segues, but even then it's an extra two or three lines of code to get it to work. See the section title "Adding prepareForSegue" here: http://makeapppie.com/2014/07/01/swift-swift-using-segues-and-delegates-in-navigation-controllers-part-1-the-template/ — chedabob, May 16 '15 at 10:16
Simplest way is found at: http://stackoverflow.com/a/28476319/1953178 — Amr Hossam, Apr 23 '16 at 10:29
take a look here: [enter link description here](https://stackoverflow.com/a/61596926/8160252) — Zouhair Sassi, May 04 '20 at 16:26

score 14 · Accepted Answer · edited Feb 05 '20 at 11:45

One easy way to achieve this you can use NSNotificationCenter for that.

In your ParentViewController add this into viewDidLoad method:

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: Selector(("refresh:")), name:NSNotification.Name(rawValue: "refresh"), object: nil)
}

After that add this function in ParentViewController which will get called when you dismiss your ChildViewController:

func refreshList(notification: NSNotification){

    print("parent method is called")
}

and into your ChildViewController add this code where you dismissing your child view:

 @IBAction func btnPressed(sender: AnyObject) {

    NotificationCenter.default.post(name: NSNotification.Name(rawValue: "refresh"), object: nil)
    self.dismiss(animated: true, completion: nil)
}

Now when you dismiss child view refreshList method will be call.

chrisamanse · Answer 2 · 2015-05-16T18:14:20.623

Add a weak property to the child view controller that should contain a reference to the parent view controller

class ChildViewController: UIViewController {
weak var parentViewController: UIViewController?
....
}

Then in your code (I'm assuming it's inside your parent view controller),

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("myChildView") as! ChildViewController
vc.parentViewController = self
self.presentViewController(vc, animated: true, completion: nil)

And, as vomako said, call the parent's method before dismissing your child view controller.

parentViewController.someMethod()
self.dismissViewControllerAnimated(true, completion: nil)

Or, you can also call the method in the completion paramter of dismissViewControllerAnimated, where it will be run after you child view controller dismisses:

self.dismissViewControllerAnimated(true) {
    parentViewController.someMethod()
}

Thanks for helping : theoretically this looks good, but I have problems practically :-). I get the error : Cannot assign to 'parentViewController' in vc. Second: — mcfly soft, May 16 '15 at 10:14
Did you cast the view controller as UIViewController or as a sublass of your UIViewController such as UIViewController? You have to subclass it if you want to have your additional properties. let vc = storyboard.instantiateViewControllerWithIdentifier("myChildView") as! **ChildViewController** — chrisamanse, May 16 '15 at 18:17

score 1 · Answer 3 · edited May 23 '17 at 12:34

1

Something that I've noticed in your question: Do not call a method (the parent method in your case) after dismissing the view controller. Dismissing the view controller will cause it to be deallocated. Later commands may not be executed.

The link that you've included in your question points to a good answer. In your case, I would use delegation. Call the delegation method in the parent view controller before you dismiss the child view controller.

Here is an excellent tutorial.

edited May 23 '17 at 12:34

Community

1
1

answered May 16 '15 at 09:40

John

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Thanks for helping. I tried to implement the solution in the good link, but I am facing a problem. With UIViewController I cant set the delegate ( child.delegate = self ). I mean I can't : vc.delegate=self. – mcfly soft May 16 '15 at 10:04
Hello, it should work. What error message do you get? – John May 16 '15 at 10:13
'UIViewController' does not have a member named 'delegate' – mcfly soft May 16 '15 at 10:16
Make sure to include a property `delegate` in the header file (.h) of your child view controller (see the tutorial link I provided under `Passing Data Back`) – John May 16 '15 at 10:18

score 1 · Answer 4 · answered May 16 '15 at 10:31

protocol SampleProtocol 
{
    func someMethod()
}   


class parentViewController: SampleProtocol 
{
    // Conforming to SampleProtocol
    func someMethod() {
    }
}

 class ChildViewController
    {
        var delegate:SampleProtocol?
    }

    self.dismissViewControllerAnimated(true, completion: nil)
    delegate?.someMethod()

calling a parent UIViewController method from a child UIViewController

4 Answers4

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