SwiftUI sheet infinite loop? - swiftui

Question

Is this a bug in SwiftUI? If you tap "Test" it goes into a loop, putting up sheet after sheet forever. I can't see why.
This is happening on iOS and iPadOS 15
struct ContentView: View {
#State private var showSheet = false
#State private var name: String = ""
#FocusState private var isFocused: Bool
var body: some View {
VStack {
Button("Test") { setState() }
}
.sheet(isPresented: $showSheet) {
VStack {
Text("\(showSheet.description), \(name)")
TextField("folder name", text: $name)
focused($isFocused)
}
}
}
private func setState() {
print("setState")
showSheet = true
}
}

Answer 1

This is a typo, and normally should be just closed as such, but I think the reason is interesting enough to warrant an answer here:
struct ContentView: View {
#State private var showSheet = false
#State private var name: String = ""
#FocusState private var isFocused: Bool
var body: some View {
VStack {
Button("Test") { setState() }
}
.sheet(isPresented: $showSheet) {
VStack {
Text("\(showSheet.description), \(name)")
TextField("folder name", text: $name)
focused($isFocused) //<-- THIS LINE IS MISSING A `.` -- it should be .focused($isFocused)
}
}
}
private func setState() {
print("setState")
showSheet = true
}
}
Because you've omitted a . on the focused line, focused is returning a modifier on ContentView itself rather than on the TextField. That means that it's adding a copy of ContentView to the view hierarchy below TextField (since focused returns a modified version of self) rather than modifying the TextField in place.
This is causing the loop, but because technically it's valid code, it doesn't generated a compiler error.