Question 185758 in IOS Swift Question posted in
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Ios swift – How to create a SwiftUI #Preview in Xcode 15 for a view with a @Binding

If I wanted to create a preview for a SwiftUI view that contains a @Binding I would have previously written something like this:

struct SpecialButton_Preview: PreviewProvider {
    static var previews: some View {
        @State var value: Bool = true
        SpecialButton(isOn: $value)
    }
}

However Xcode 15 now comes with a new syntax (#Preview) but when I try to add my example state property, it does not work:

#Preview {  // Error: Ambiguous use of 'Preview(_:traits:body:)'
    @State var value: Bool = true
    SpecialButton(isOn: $value)
}

How can I make this work?

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2

Answers


  1. 0

    What you could do before and still can do is:

    SpecialButton(isOn: .constant(true))
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  2. 0

    You need to return the View to preview. I’m not exactly sure how this works, it has to do with how Swift macros work.

    #Preview {
    @State var value: Bool = true
    return SpecialButton(isOn: $value)
}

    From the WWDC Slack:
    "The new #Previews macro simply takes a closure that returns the thing to be previewed. So you can declare local variables or do other setup necessary in there just like you would in any other closure."

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