How to use an NSAttributedString with a ScrollView in SwiftUI?

Question

I\'ve been able to render NSAttributedStrings via UIViewRepresentable which works great until I wrap the view in a ScrollView.

<

Answer 1

If you want to use Asperi's TextWithAttributedString as a child view, replace

height = textView.sizeThatFits(UIScreen.main.bounds.size).height

by

DispatchQueue.main.async {
    height = textView.sizeThatFits(textView.visibleSize).height
}

Answer 2

The reason is that SwiftUI ScrollView requires defined content size, but used UITextView is itself a UIScrollView and detects content based on available space in parent view. Thus it happens cycle of undefined sizes.

Here is a simplified demo of possible approach how to solve this. The idea is to calculate content size of UITextView and pass it to SwiftUI...

struct TextWithAttributedString: UIViewRepresentable {
    @Binding var height: CGFloat
    var attributedString: NSAttributedString

    func makeUIView(context: Context) -> UITextView {
        let textView = UITextView(frame: .zero)
        textView.isEditable = false
        return textView
    }

    func updateUIView(_ textView: UITextView, context: Context) {
        textView.attributedText = self.attributedString

        // calculate height based on main screen, but this might be 
        // improved for more generic cases
        DispatchQueue.main.async { // << fixed 
            height = textView.sizeThatFits(UIScreen.main.bounds.size).height
        }
    }
}


struct NSAttributedStringView: View {
    @State private var textHeight: CGFloat = .zero
    var body: some View {
        ScrollView {
            TextWithAttributedString(height: $textHeight, attributedString: NSAttributedString(string: exampleText))
                .frame(height: textHeight) // << specify height explicitly !
        }
    }
}