Deleting list elements from SwiftUI’s List

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Using insights from @pawello2222 and @Asperi, I came up with an approach that I think works well, without being overly nasty (still kinda hacky).

I wanted to make the approach more general than just for the simplified example in the question, and also not one that breaks separation of concerns.

So, I created a new wrapper view that creates a binding to an array element inside itself (which seems to fix the state invalidation/update ordering as per @pawello2222’s observation), and passes the binding as a parameter to the content closure.

I initially expected to be needing to do safety checks on the index, but turns out it wasn’t required for this problem.

struct Safe<T: RandomAccessCollection & MutableCollection, C: View>: View {
   
   typealias BoundElement = Binding<T.Element>
   private let binding: BoundElement
   private let content: (BoundElement) -> C

   init(_ binding: Binding<T>, index: T.Index, @ViewBuilder content: @escaping (BoundElement) -> C) {
      self.content = content
      self.binding = .init(get: { binding.wrappedValue[index] }, 
                           set: { binding.wrappedValue[index] = $0 })
   }
   
   var body: some View { 
      content(binding)
   }
}

Usage is:

@ObservedObject var vm: ViewModel = .init()

var body: some View {
   List(vm.arr.indices, id: \.self) { index in
      Safe(self.$vm.arr, index: index) { binding in
         Toggle("", isOn: binding)
         Divider()
         Text(binding.wrappedValue ? "on" : "off")
      }
   }
}

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