Cannot convert value of type 'TupleView<(Text, Text)>' to closure result type 'Text'

Question

I am trying to understand why I keep getting an error when I try to use this custom layout view I've created.

Here is the error (also commented in the code below):

Cannot convert value of type 'TupleView<(Text, Text)>' to closure result type 'Text'

And here is the code that generates the problem.

struct BaseRecordView_Previews: PreviewProvider {
    static var previews: some View {

        // Error: Cannot convert value of type 'TupleView<(Text, Text)>' 
        // to closure result type 'Text'
        BaseRecordView() { 
            Text("125.6")
            Text("kg")
        } subHeading: {
            Text("44.1 BMI")
        } content: {
            Text("Something here")
        }

    }
}

and this is how I have defined BaseRecordView:

struct BaseRecordView<Content: View>: View {
    @ViewBuilder var heading: Content
    @ViewBuilder var subHeading: Content
    @ViewBuilder var content: Content
    
    init(
         @ViewBuilder heading: @escaping () -> Content,
         @ViewBuilder subHeading: @escaping () -> Content,
         @ViewBuilder content: @escaping () -> Content)
    {
        self.heading = heading()
        self.subHeading = subHeading()
        self.content = content()
    }
    
    var body: some View {
        // layout content here
        heading
        subHeading
        content
    }
}

What am I missing here? What is the meaning of TupleView<(Text, Text)> in this context?

Answer 1

The problem is that you declared your BaseRecordView with all 3 of its generic View properties having the same Content type, but you are passing a different type of view to heading that to subHeading and content.

If you want to be able to pass 3 different types of Views, you need 3 different generic type parameters.

struct BaseRecordView<Heading: View, Subheading: View, Content: View>: View {
    @ViewBuilder private let heading: Heading
    @ViewBuilder private let subHeading: Subheading
    @ViewBuilder private let content: Content

    init(
         @ViewBuilder heading: @escaping () -> Heading,
         @ViewBuilder subHeading: @escaping () -> Subheading,
         @ViewBuilder content: @escaping () -> Content)
    {
        self.heading = heading()
        self.subHeading = subHeading()
        self.content = content()
    }

    var body: some View {
        // layout content here
        heading
        subHeading
        content
    }
}

struct BaseRecordView_Previews: PreviewProvider {
    static var previews: some View {

        // Error: Cannot convert value of type 'TupleView<(Text, Text)>'
        // to closure result type 'Text'
        BaseRecordView() {
            Text("125.6")
            Text("kg")
        } subHeading: {
            Text("44.1 BMI")
        } content: {
            Text("Something here")
        }

    }
}