Remove onDismiss closure call when dismissing presentedViewController

[woohyunjin06]

onDismiss closure is being called even when the presentedViewController is dismissed.
As far as I understand, the onDismiss closure should only be called when the ViewController passed as the content closure is dismissed.

[stephencelis]

@woohyunjin06 Thanks for taking the time to explore. I think that onDismiss is the behavior we want, though. That branch is dismissing the current view controller before presenting a new one for a new destination. The behavior matches SwiftUI:

import SwiftUI

struct Item: Identifiable {
  let id = UUID()
}

struct ContentView: View {
  @State var destination: Item?

  var body: some View {
    VStack {
      Button("Sheet") {
        destination = Item()
      }
    }
    .sheet(item: $destination) {
      print("onDismiss")
    } content: { item in
      Button("Another sheet") {
        destination = Item()
      }
    }
  }
}

#Preview {
  ContentView()
}

If you run the code above and tap "Sheet", and then tap "Another sheet", you will see "onDismiss" print in the console between the dismissal and presentation.

Since I believe the current behavior is what we want I'm going to close this out, but if I'm missing something or you can demonstrate an issue with a unit test, please let me know!

[woohyunjin06]

Hi @stephencelis !
To demonstrate the issue, I modified the ConciseEnumNavigationViewController.swift as follows:

present(isPresented: UIBinding($model.destination.sheet1))  {
  print("onDismiss sheet1")
} content: {
  let vc = UIHostingController(
    rootView: Form {
      Text("Sheet 1")
    }
  )
  vc.mediumDetents()
  return vc
}
present(isPresented: UIBinding($model.destination.sheet2)) {
  print("onDismiss sheet2")
} content: {
  let vc = UIHostingController(
    rootView: Form {
      Text("Sheet 2")
      Button("Present Sheet 1") {
        self.model.destination = .sheet1
      }
    }
  )
  vc.mediumDetents()
  return vc
}​

When running this code, you can see that onDismiss sheet1 is printed in console when presenting "Sheet 1" from "Sheet 2" even though Sheet 1 hasn’t actually been dismissed.
https://github.com/user-attachments/assets/9f3f64f1-a5f6-45a8-ae4e-a032669e6584

This behavior differs from the results when performing the same actions in SwiftUI.
https://github.com/user-attachments/assets/962f9b5e-9b3b-4cd5-99c1-4c57b9303a0f

it seems that simply removing the onDismiss call is not the right way to solve this issue, but I think the current behavior of onDismiss closure is definitely a bit weird.

Full code: https://gist.github.com/woohyunjin06/399e863766803ce64e68c2a76d74050f

[stephencelis]

@woohyunjin06 Thanks for the repro! I understand the problem now and have captured it in a test here: #242