Issue in Setting Value to #State variable in SwiftUI [duplicate] - swiftui

Question

Hello I am running into a problem here and I do not have a consistent behavior between my .sheet() view when running on ios13 or ios14
I got a view like this :
#State private var label: String = ""
#State private var sheetDisplayed = false
///Some code
var body: some View {
VStack {
Button(action: {
self.label = "A label"
self.isDisplayed = true
}) {
Text("test")
}
}.sheet(isPresented: $sheetDisplayed, onDismiss: {
self.label = ""
}) {
Text(self.label)
}
}
On ios 13 this work as expected btn click -> set label -> call sheet -> display "A label" in a Text view.
On ios14 I got an empty string in self.label when in sheet closure, hence it does not display anything.
Did I missed something ? Is it an iOS 14 bug or did I had it wrong on ios13 and that got corrected.
PS: I have a couple of other variables that are passed in the closure I simplified it.

Answer 1

Your code have expectation of view update/creation order, but in general it is undefined (and probably changed in iOS 14).
There is explicit way to pass information inside sheet - use different sheet creator, ie. .sheet(item:...
Here is working reliable example. Tested with Xcode 12 / iOS 14
struct ContentView: View {
#State private var item: Item?
struct Item: Identifiable {
let id = UUID()
var label: String = ""
}
var body: some View {
VStack {
Button(action: {
self.item = Item(label: "A label")
}) {
Text("test")
}
}.sheet(item: $item, onDismiss: {
self.item = nil
}) {
Text($0.label)
}
}
}

Answer 2

This is some really strange behaviour in iOS 14, which doesn't appear to be documented.
Using the other answer here and the comment on this thread, I used #Binding to solve the issue as it seemed the cleanest and most SwiftUI-esq solution.
I have no idea why this behaviour has changed, and it seems less intuitive than before, so I'm assuming its a bug!
An example:
struct MainView: View {
#State private var message = ""
#State private var showSheet = false
var body: some View {
Button(action: {
self.message = "This will display the correct message"
self.showSheet = true
}, label: {
Text("Test Button")
})
.sheet(isPresented: self.$showSheet) {
SheetView(message: self.$message)
}
}
}
struct SheetView: View {
#Binding var message: Int
var body: some View {
Text(self.message)
}
}

Answer 3

The behaviour changed with SwiftUI 2.0, so it affects MacOS 11 as well, just adding a binding to the view fixes it even when that binding is never used, which makes me think this is an implementation bug.
Additionally just using the details state variable in a Text() within the body of the view also fixes it.
struct MyViewController : View {
#State var details: String?
#State var showDetails = false
// #Binding var havingAbindingFixesIt: String?
var body: some View {
VStack {
// Text(details ?? "")
Text("Tap here for details")
.onTapGesture {
self.details = "These are the details"
self.showDetails.toggle()
}
.sheet(isPresented: $showDetails) { Text(details ?? "") }
}
}
}