How can I prevent the modal content from going empty while the dismiss animation is still ongoing?

[Jager-yoo]

Hey everyone! 👋🏻
I've encountered an issue when using SwiftUI's sheet or fullScreenCover with an optional state and IfLetStore.
Whenever I dismiss the modal programmatically, its content immediately turns 'empty'.

This is because the IfLetStore re-computes its content depending on if an optional state is nil or non-nil.

For reference, please check out the following recording.
I used a sheet example from SwiftUICaseStudies and simply added a dismiss button using @Environment(\.dismiss) along with a black background for better contrast.

.sheet(
  isPresented: viewStore.binding(
    get: \.isSheetPresented,
    send: LoadThenPresent.Action.setSheet(isPresented:)
  )
) {
  IfLetStore(
    self.store.scope(
      state: \.optionalCounter,
      action: LoadThenPresent.Action.optionalCounter
    )
  ) {
    CounterView(store: $0) // This is the ⬛️ page, and turns empty when dismiss() is called
  }
}

sheet.with.IfLetStore.mp4

Does anyone have a good solution for maintaining the modal content while the dismiss animation is in progress? 🤔
What's the best way to present modal content that has an optional state?

[tgrapperon]

Hey @Jager-yoo! There is a returningLastNonNilValue utility in that you can use to keep presenting the last non-nil value of State.
Please note that the upcoming navigation utilities will handle this automatically.

[Jager-yoo]

Oh wow, returningLastNonNilValue is so useful when presenting optional state!
I'll use this as ad hoc solution until navigation 1.0 comes out! Thanks as always. 👍🏻

.sheet(
  isPresented: viewStore.binding(
    get: \.isSheetPresented,
    send: LoadThenPresent.Action.setSheet(isPresented:)
  )
) {
  IfLetStore(
    self.store.scope(
      state: returningLastNonNilValue { $0.optionalCounter }, // ✨applied here!
      action: LoadThenPresent.Action.optionalCounter
    )
  ) {
    CounterView(store: $0)
  }
}

sheet.with.returningLastNonNilValue.mp4

[Jager-yoo]

However, I'm still wondering why returningLastNonNilValue was implemented as an open function.
Could we wrap it within some extension instead?

[tgrapperon]

I can't say for sure, but my guess is that the free function is more lightweight and generic than an extension, and it makes the storage simple enough in this "surrounding" position.

[Jager-yoo]

Thank you for your help!