SwiftUI: Preventing binding value from passing back up?

in the Secondary struct, the @Binding property is secondTime and I want it to initially have the value from the "parent".
But when I change the value in this struct, the time property in the parent also changes. Is there a way to get the value from the parent but prevent any changes to the value from going back up to the parent?

struct ContentView: View {
   
    @State var time: String = "";
    
    var body: some View {
        
        VStack {

            Text("it is: \(time)")
            
            Secondary(secondTime: $time)
            
            Button("Change time") {
                time = "2 poclock"
            }
        }
    }
}

struct Secondary: View {
    @Binding var secondTime: String;
    
    var body: some View {
        Text("secondary time is \(secondTime)")
        
        Button("Change time again from Secondary View") {
            secondTime = "3 oclock"
        }
    }
}

SwiftUI: Preventing binding value from passing back up?

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0 Answer

david1202 注册会员
2023-01-26 02:39

In Secondary use:

@State var secondTime: String

and in ContentView use:

Secondary(secondTime: time)

not $time

EDIT1:

If you want to click the button in ContentView to change both views, but Secondary only changes itself, then try this approach:

struct Secondary: View {
    @Binding var secondTime: String
    @State var localTime: String = ""
    
    var body: some View {
        Text("Secondary time is \(localTime)")     // <--- here
            .onChange(of: secondTime) { newval in  // <--- here
                localTime = newval                 // <--- here
            }
        Button("Change time again from Secondary View") {
            localTime = "3 oclock " + String(Int.random(in: 1..<100)) // <-- to show changes
        }
    }
}
    
    struct ContentView: View {
        @State var time: String = ""
        
        var body: some View {
            VStack (spacing: 55) {
                Text("ContentView it is: \(time)")
                Secondary(secondTime: $time)
                Button("Change time") {
                    time = "2 oclock " + String(Int.random(in: 1..<100))  // <-- to show changes
                }
            }
        }
    }