Sheet doesn't open when triggered in onAppear

Question

I've encountered a strange bug when a sheet doesn't open if triggered in onAppear.

The following does not trigger the sheet in Xcode 12.3, iOS 14.3:

struct ContentView: View {
    @State private var sheetActive = false

    var body: some View {
        Text("Test")
            .sheet(isPresented: $sheetActive) {
                Text("Sheet")
            }
            .onAppear {
                sheetActive = true
            }
    }
}

The sheet only pops up after I interact with the screen in any way.

However, if I wrap Text in NavigationView / List etc. it does work.

Also, even attaching a simple modifier (like onChange) triggers the sheet:

struct ContentView: View {
    @State private var sheetActive = false

    var body: some View {
        Text("Test")
            .sheet(isPresented: $sheetActive) {
                Text("Sheet")
            }
            .onAppear {
                sheetActive = true
            }
            .onChange(of: sheetActive) {
                print($0)
            }
    }
}

It also works when I trigger the sheet asynchronously:

struct ContentView: View {
    @State private var sheetActive = false

    var body: some View {
        Text("Test")
            .sheet(isPresented: $sheetActive) {
                Text("Sheet")
            }
            .onAppear {
                DispatchQueue.main.async {
                    sheetActive = true
                }
            }
    }
}

Is this a bug in iOS 14.3 or some intended change I'm not aware of?

Answer 1

If you change your sheetActive to true it should open upon initialization.

The bugs of using onAppear() to initialize/active stuff are constantly being mentioned in SO and the Apple forums. It is very unreliable.

struct ActiveSheetView: View {
    @State private var sheetActive = true
    var body: some View {
        Text("Test")
            .sheet(isPresented: $sheetActive) {
                Text("Sheet")
            }
    }
}