SwiftUI attributed string from HTML crashes the app

Question

I'm trying to convert HTML formatted text into an attributed string, and insert it into a SwiftUI view.

Firstly I have a String extension that converts the HTML string to NSAttributedString:

extension String {
    func convertHtml() -> NSAttributedString {
        guard let data = data(using: .utf8) else { return NSAttributedString() }

        if let attributedString = try? NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil) {
            return attributedString
        } else {
            return NSAttributedString()
        }
    }
}

Then I have created a HTMLLabel view:

struct HTMLLabel: UIViewRepresentable {

    let html: String

    func makeUIView(context: UIViewRepresentableContext<Self>) -> UILabel {
        let label = UILabel()
        label.attributedText = html.convertHtml()

        return label
    }

    func updateUIView(_ uiView: UILabel, context: UIViewRepresentableContext<Self>) {}

}

Then I insert a test into my SwiftUI view:

HTMLLabel(html: "<html><body><b>Hello</b> <i>World</i></body></html>")

The code crashes each time on if let attributedString = try? ... with EXC_BAD_INSTRUCTION. I made a test in an empty storyboard project like this:

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        let label = UILabel(frame: CGRect(x: 50, y: 50, width: 320, height: 50))
        label.attributedText = "<html><body><b>Hello</b> <i>World</i></body></html>".convertHtml()

        view.addSubview(label)
    }
}

That code executes without any issues. Why doesn't the code work in a SwiftUI context?

Pushpendra · Accepted Answer · 2020-01-14 10:48:32Z

13

Use This:-

struct HTMLLabel: UIViewRepresentable {

let html: String

func makeUIView(context: UIViewRepresentableContext<Self>) -> UILabel {
    let label = UILabel()
    DispatchQueue.main.async {
        if let attributedText = self.html.convertHtml() {
               label.attributedText = attributedText
            }
    }

    return label
}

func updateUIView(_ uiView: UILabel, context: UIViewRepresentableContext<Self>) {}

}

NSAttributedString.DocumentType.html is Only Work with Main Thread That's why you are getting crash

edited Jan 14, 2020 at 10:48

answered Jan 14, 2020 at 10:29

Pushpendra

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