当 UIViewController 返回顶部时，iOS 中是否有委托函数来获得通知？

Question

I'm somewhat a Swift/iOS newbie but this seems simple. I have a UIViewController and upon some action I am instantiating another modal UIViewController, which at some point I will dismiss. I just need to originating VC to be notified when this happens. Realizing that this could be handled using navigation control, I'm looking for a way to do it modally ie

I want to push the modal vc on to the hierarchy:

let vc = storyboard.instantiateViewController(withIdentifier: "DetailView")
self.present(vc, animated: true, completion: nil)

and when I do this in the modal vc:

dismiss(animated: true, completion: nil)

I just want the original vc sitting in the background to be notified it's coming back into focus (or top) and be able to execute code.

What am I missing?

Answer 1

UPDATED : the answer here is very simple. A ViewController that is presented modally with a presentation style of "Over Current Context" does not fire ViewWillAppear in the presenting VC when it is dismissed. The answer below worked fine as a hack, but the easier solution is what I was looking for. That is, changing the presentation style to Full Screen.

---

So I ended up implementing a compact solution - some will say that it's not OOP without the protocol, and I agree - but in the scope of this app, it solves the problem in the context of a simple present/dismiss construct.

In the presenting vc, I added this code.

let vc = storyboard.instantiateViewController(withIdentifier: "DetailView") as! DetailViewController
vc.masterVC = self
self.present(vc, animated: true, completion: nil)

The declared a function in the masterVC to be called when the modal dismisses ie:

func calledWhenModalDismisses() {
   // Do This
}

In the modal DetailView that pops up, I just create a member pointing to the master:

var masterVC: MasterViewController?

And then in my detail dismissal function, I can call back to the function I created in the MasterVC.

masterVC?.calledWhenModalDismisses()
dismiss(animated: true, completion: nil)

Again, not a truly OOP solution (without the protocol) but I'm sure this will help someone with a simple compact solution to a simple master/detail issue when the presenting vc needs to be alerted as the detail vc is being dismissed. Apple should actually have a delegate function to handle this when a vc comes into "focus" but they do not.