SwiftUI View Builder parameter cannot change state

Question

I am trying to create a SwiftUI view where I can pass a view builder. But by using a view builder parameter I cannot change the state. Is this due to the creation in the init method? How can I achieve my expected behaviour?

struct Card_Previews: PreviewProvider {
    
    @State
    static var bol: Bool = true
    static var previews: some View {
        Label(title: { content })
    }
    
    // Does not change the value
    private static var content: some View {
        Button(bol.description) {
            bol.toggle()
        }
    }
}


struct Label<Title>: View where Title: View {

    var body: some View {
        title
    }

    let title: Title
    public init(@ViewBuilder title: () -> Title) {
        self.title = title()
    }
}

If something is unclear pleas ask :)

score 1 · Accepted Answer · answered Aug 01 '22 at 11:35

1

Your problem is unrelated to @ViewBuilder, it's because bol is a State & not Binding. To solve this you need to bind the 2 properties like so:

struct Label<Title>: View where Title: View {

    @Binding
    var bol: Bool
    
    var body: some View {
        HStack {
            title
            Button(bol.description) {
                // Changes the value
                bol.toggle()
                print(bol.description)
            }
        }
    }
    
    let title: Title
        
    
    public init(bol: Binding<Bool>, @ViewBuilder title: () -> Title) {
        self.title = title()
        self._bol = bol
    }
}

And in Card_Previews replace Label(title: { content }) with Label(Bol: $bol, title: { content }).

answered Aug 01 '22 at 11:35

Timmy

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Hmm this doesn't seem to work either. :( – Tbi Aug 01 '22 at 11:42
why is bol static in the preview? – Timmy Aug 01 '22 at 11:51
yes. that was the problem. thank you so much. I was just so focused on the @State that I overlooked the static. – Tbi Aug 01 '22 at 11:55
I don't know how we can now get a accepted answer or if I should just delete it. – Tbi Aug 01 '22 at 11:55
1

It's Your call! – Timmy Aug 01 '22 at 11:57

SwiftUI View Builder parameter cannot change state

1 Answers1