Laggy typing and cursor jumps with TextField? - ios

Question

My app uses TextFields everywhere to modify CoreData entities' String attributes. They work very poorly - typing a space or getting an auto correct event seems to make the cursor jump to the end of the window. Keystrokes are missed and the whole experience is laggy. TextEditors, on the other hand, work fine. The behavior doesn't appear on the simulator, only on (multiple) real devices.
What am I doing wrong here? Am I using TextFields wrong?
Code is below, it's basically the starter Xcode app with a "text: String?" attribute added to the "item" CoreData entity.
struct Detail: View {
#ObservedObject var item: Item
var body: some View {
VStack {
Form {
Section(content: {
TextField("Title", text: $item.text ?? "")
}, header: {
Text("TextField")
})
Section(content: {
TextEditor(text: $item.text ?? "")
}, header: {
Text("TextEditor")
})
}
}
}
}
// Optional binding used
func ??<T>(lhs: Binding<Optional<T>>, rhs: T) -> Binding<T> {
Binding(
get: { lhs.wrappedValue ?? rhs },
set: { lhs.wrappedValue = $0 }
)
}
Update:
I ended up just putting the TextFields into a subview and then writing their value back to the NSManagedObject via a binding every time the value changes.
I have no idea why, but this fixes the problem for me.
struct CustomTextField: View {
#Binding var string: String?
#State var localString: String
let prompt: String
init(string: Binding<String?>, prompt: String) {
_string = string
_localString = State(initialValue: string.wrappedValue ?? "")
self.prompt = prompt
}
var body: some View {
TextField(prompt, text: $localString, axis: .vertical)
.onChange(of: localString, perform: { _ in
string = localString
})
}
}

Answer 1

Example of using onSubmit, which does not cause CoreData to save the data on every input by the keyboard.
struct Detail: View {
#ObservedObject var item: Item
#State var text: String = "" // for starting with an empty textfield
// Alternative if you want the data from item:
// #State var text: String = item.text.wrappedValue // This only works if text is a binding.
var body: some View {
VStack {
Form {
Section(content: {
TextField("Title", text: $text)
.onSubmit {
item.text = self.text
}
}, header: {
Text("TextField")
})
Section(content: {
TextEditor(text: $text)
.onSubmit {
item.text = self.text
}
}, header: {
Text("TextEditor")
})
}
}
}
}
If that does not help, it would be nice to know how Item looks like.