Pass Binding<String> to UserDefaults-Swift

Question

I created a watchos App that asks the user for his weight and want to store the weight's value in Userdefaults. The code is as follows

...
@State var weight: String = ""
        var body: some View {
                ScrollView{
                VStack(alignment: .leading) {
                    TextField("Enter height...", text: $weight)
                        .onAppear(){
                            UserDefaults.standard.setValue(weight, forKey: "userWeight")}
                            ...
        }
     }

When I read the userdefaults userweight is "".