SwiftUI connecting #Binding to #Published directly in ChildView - swiftui

Question

We needed to bind to the #Published in a ParentView's #StateObject being used as a ViewModel. I told my coworker we needed to pass in the entire ViewModel to an #ObservedObject in the ChildView, since everything I've read about SwiftUI describes the parent-child data relationships like this:
Parent View
Child View
#State
#Binding
#StateObject
#ObservedObject
#Published (within the #StateObject)
DOESN'T EXIST
He insisted we could just pass in the #Published alone to the ChildView's #Binding and it would work. Lo and behold, he was right. In the example code below is the documented way to use #Binding, along with passing the entire #StateObject down into an #ObservedObject and binding to the #Published directly (which I thought was the only way you could/should bind to an #Published), and passing the #Published directly into the #Binding, which surprisingly does work. You can see in the sample pic that when you type in any of the 3 TextField's, the updates appear immediately in the parent view, proving that the #Binding works with all 3 approaches.
Is this a fluke about binding to the #Published directly? Or an undocumented-but-valid approach? Why isn't this taught as a standard approach?
import SwiftUI
class MyViewModel: ObservableObject {
#Published var publishedStr1 = "I am publishedStr1"
#Published var publishedStr2 = "I am publishedStr2"
}
struct ParentView: View {
#State var stateStr = "I am stateStr"
#StateObject var myViewModel = MyViewModel()
var body: some View {
VStack {
ChildView(stateStr: $stateStr,
myViewModel: myViewModel,
// Why don't I ever see examples using this technique
// of passing the #Published directly to an #Binding?
// It clearly works.
publishedStr2: $myViewModel.publishedStr2)
Text(stateStr)
Text(myViewModel.publishedStr1)
Text(myViewModel.publishedStr2)
}
}
}
struct ChildView: View {
#Binding var stateStr: String
#ObservedObject var myViewModel: MyViewModel
#Binding var publishedStr2: String
var body: some View {
VStack {
TextField("Binding to State", text: $stateStr)
.textFieldStyle(RoundedBorderTextFieldStyle())
TextField("Binding to ObservedObject",
text: $myViewModel.publishedStr1)
.textFieldStyle(RoundedBorderTextFieldStyle())
TextField("Binding to ObservedObject's Published",
text: $publishedStr2)
.textFieldStyle(RoundedBorderTextFieldStyle())
}
}
}

Answer 1

#StateObject is only when we need a reference type for state. In your case you don't so just use #State, e.g.
struct ParentViewConfig {
var publishedStr1 = "I am publishedStr1"
var publishedStr2 = "I am publishedStr2"
var stateStr = "I am stateStr"
mutating func someFunc() {
}
}
struct ParentView: View {
#State var config = ParentViewConfig()