ForEach Breaks Data Binding

UPDATE - right after posting this I found a solution (See adding HStack comments at the end of discussion):

https://forums.developer.apple.com/message/412141#412141

So, this code works and I have no idea why:

ForEach(noise.twoControlEffects.indices){ i in
     VStack{
          if(self.noise.twoControlEffects[i].isDisplayed){
               TwoControlTemplate(title: "Low Pass Filter",
                                   isBypassed: self.$noise.twoControlEffects[i].isBypassed,
                                   knobModel1: self.$noise.twoControlEffects[i].control1,
                                   knobModel2: self.$noise.twoControlEffects[i].control2)
          }
     }
}

Apparently, you just have to wrap the inside of your ForEach code in a HStack or VStack.

Jeez... I could have looped infinitely without your suggestion... Thanks, it does work indeed, and it saves my evening...

Is anyone from Apple planning on addressing this issue? It seems to me that control statements in general are breaking data binding. And this in my opinion is a show stopper.

Apple... Please the least that you can do, even if you don't want to fix it, or feel it's "as design" is shed some light on the problem and give us an explanation so we understand this better.

It seems to me that control statements in general are breaking data binding. And this in my opinion is a show stopper. 

I'd love to explore this further with you if you're still around, abzy! There are some gotchas to working with control statements, especially in situations like this, where the types of views you are passing in get involved, but they generally do not break data binding at all as long as you're aware of how the views are being used.

In the example above, I think the big problem is that when you loop over an object in SwiftUI, you need it to return something every single time. This is sort of a consequence of the way that Swift's syntax around builders works. So wrapping it in something like a group or stack works, but it would also work to wrap it in a special kind of view that actually does have the power to contain any number of elements, and you do that with @ViewBuilder.

So you could make something like:

Code Block 
struct ConditionalTwoControl: View {
	@Binding var effect: TwoControlEffect
	@ViewBuilder var body: some View {
		if effect.isDisplayed {
			TwoControlTemplate(title: "Low Pass Filter",
																	 isBypassed: $effect.isBypassed,
																	 knobModel1: $effect.control1,
																	 knobModel2: $effect.control2)
		}		
	}
}

and then have that ForEach look like:

Code Block 
ForEach(noise.twoControlEffects.indices){ i in
		 ConditionalTwoControl(effect: self.$noise.twoControlEffects[i]) 
}

And this would also work (with a little situational tweaking, of course).

More at hand to the situation here, I would consider trying to avoid looping over just an index if you can find a way around that, especially if you can just make your object conform to Identifiable. That's going to give you much more straightforward results with much more trace-able data binding.

I'm having similar trouble, but unfortunately iterating on the indices and passing an array item with subscript won't work for me. My ForEach statement iterates on the struct's name field and simultaneously sorts the array:

                    ForEach(store.cocktails.sorted {$0.cocktailName < $1.cocktailName }) { ******** in
                        CocktailCell(********: $********)
                    }

I don't want to give up the automatic sort, hence, I cannot access the index each time through in order to send a single array item. I do, however, have to pass a binding for the item because at each level below I either want to read the values in the struct or write to them.

The object "store" is instantiated with @StateObject at the parent level, and passed in as an ObservedObject at this view level.
Any ideas?

Jeez, that didn't post too well...replace the ******* in each case with the word c*ocktail. Ridiculous level of "disallow listing" words.

Running into a similar problem, if a value changes the entire text for the particular key value pair disappears:

Code Block 
ForEach(viewCounts.sorted(by: <), id: \.key) { key, value in
		Text("\(key) \(value)")
}

arithMattic You're a life saver! It's weird.

"Apparently, you just have to wrap the inside of your ForEach code in a HStack or VStack."

weird way to fix it all but hey it gets the job done!

I was having a similar issue when trying to create NavigationLinks inside of a ForEach loop. The destination View had random data from the iterative object (lesson in my case).

Code Block 
            ForEach(viewModel.additionalLessons) { lesson in
                    NavigationLink(
                        destination: LessonView(viewModel: LessonViewModel(lesson: lesson,
                        isSelected: $viewModel.lessonSelected)),
                        isActive: $viewModel.lessonSelected,
                        label: {
                            LessonRow(lesson: lesson)
                        })
            }

I found both embedding it into a VStack AND removing the "isActive" parameter on the NavigationLink allowed me to Bind the iterative object (lesson) into my destination view. Now I consistently get an appropriate detail view on the row I select.

Code Block 
      LazyVStack(spacing:0) {
          ForEach(viewModel.bookLessons) { lesson in
                    NavigationLink(
                        destination:
							 LessonView(viewModel: 	         LessonViewModel(lesson: lesson, 
	                             isSelected: $viewModel.lessonSelected)),
                        label: {
                            LessonRow(lesson: lesson)
                        })
               }
    	}

The ForEach View cannot not work with indicies for dynamic data, it requires identifiers which is why we supply it with an array of Identifiable data.

This is so that it can calculate inserts, moves and deletions which obviously is impossible with an array of indicies which will in the case of moving 5 items around the indices will still be 0-4.

I had the same problem: A non-updating list. The problem was: The identifiable id (representing a database ID) of each element wasn't changing, but other content of the element. So I just added a SwiftUI id to the element enclosing View, like so:

ForEach(elements) {element in
  Button {
    ... actions ...
  } label: {
    MyView(content: element)
    .id("\(element.id)\(element.changingStuff.description)")
  } 
}

That solved the problem.