The compiler is unable to type-check Button this expression in reasonable time;

[saroar]

I am not sure it bug or my code issue
issue is when I am trying send action from view inside multiple bool condition
WordTodoView.swift line number 192

[tgrapperon]

Hey @saroar! The ViewBuilder can sometimes have difficulties resolving complex views, especially when multiple conditional are chained. In this case, you can probably help him a little by wrapping your if viewStore… block in a Group.

Group {
  if viewStore … {
    …
  }
}

[mbrandonw]

Another option, in addition to @tgrapperon's suggestion, is to use @ObservedObject instead of WithViewStore, which we describe here.

I also tried compiling this code pointed to a branch with the 12 deprecated inits on WithViewStore removed and somehow it didn't make a difference. Has me second guessing whether those inits were ever problematic. I thought we had confirmed that in a sample project.

[mbrandonw]

Wow, bringing back Content: View and removing the deprecated non-observe: inits still doesn't fix the problem. Here's the branch I'm targeting.

[tgrapperon]

This is also really odd: on main, if you remove the reference to viewStore in the Button's action, it builds:

let takeQuiz: () -> Void = { viewStore.send(.takeQuiz) }
if viewStore.isActive && !viewStore.isComplete {
  HStack {
    Button {
      takeQuiz()
    } label: {
      Text("Take Quiz!")
    }
  }
}

If you simply replace the Button's action by a lone viewStore that does nothing, it doesn't build anymore. I'm not sure what's going on here, because this thing doesn't change the generic signature of the View.

[tgrapperon]

This is even weirder. This builds:

if true {
  let _ = viewStore
  HStack {
    Color.red
  }
}       

This also builds, but it takes considerably longer:

if true {
  HStack {
    let _ = viewStore
    Color.red
  }
}  

If we replace let _ = viewStore by let action: () -> Void = { viewStore.send(.takeQuiz) }, it still builds in the first case, but fails in the second. If we replace by let action: () -> Void = { }, it builds instantly in both cases.

[mbrandonw]

While messing around with this we discovered that giving an explicit type to the view store vended by WithViewStore also greatly helps:

WithViewStore(self.store, observe: { $0 }) { (viewStore: ViewStoreOf<WordTodo>) in
  …
}

So that is another alternative if one does not want to use @ObservedObject. We are going to update the performance article.

[Alex293]

I tend to rely on the explicit type when things get out of control and it’s working great

[saroar]

I am big fan of @ObservedObject yes it fixe issue @mbrandonw @tgrapperon @stephencelis thanks

[Alex293]

Be careful though as this will redraw the entire view IIRC

[saroar]

what is view IIRC ? @Alex293
so if I will use inside view ViewState ?

[Alex293]

If I remember correctly, sorry for that. Using @Viewstate at the view level will redraw the entier view. You need to make a subview if you want to avoid that. @mbrandonw

[tgrapperon]

In any case, you should always use a ViewState if your state contains superfluous data for the View. If the ViewStore is installed as an @ObservedObject, it will indeed invalidate the whole body, but this is very similar to what already happens if your WithViewStore is a top-level View in body, so it isn't really worse in terms of performance (it is even very slightly better than a top-level WithViewStore given the current implementation).
What this prevents is narrowing the ViewStore's reach to only a portion of your View, which is something possible with a WithViewStore used in a non top-level position. But this is less frequently used.