Cannot convert value of type NSAttributedString.DocumentAttributeKey to .DocumentReadingOptionKey

Question

I found this string extension somewhere on SO that allows me to turn html code into an attributed string:

func html2AttributedString() -> NSAttributedStri         


        

Answer 1

swift 4 : I dont know why all the answers have compiler error for me. so use this extension:

extension String {
    var html2AttributedString: NSAttributedString? {
        do {
            return try NSAttributedString(data: data(using: String.Encoding(rawValue: String.Encoding.utf8.rawValue))!,
                                          options: [.documentType: NSAttributedString.DocumentType.html,
                                                    .characterEncoding: String.Encoding.utf8.rawValue],
                                          documentAttributes: nil)
        } catch {
            print("error: ", error)
            return nil
        }
    }
    var html2String: String {
        return html2AttributedString?.string ?? ""
    }
}

how to use ?

mylable.text = htmlVariable.html2String

Answer 2

Swift 4.x & 5.x

if let rtfPath = Bundle.main.url(forResource: "FileName", withExtension: "rtf") {
        do {
            let attributedString: NSAttributedString = try NSAttributedString(url: rtfPath, options: [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.rtf], documentAttributes: nil)
            debugPrint(attributedString)
        } catch {
            print("Error while reading the file - \(error.localizedDescription)")
        }
 }

Getting NSAttributedString from file will be changed in Swift 3.x which is as below:

let attributedStringWithRtf: NSAttributedString = try NSAttributedString(url: rtfPath, options: [NSDocumentTypeDocumentAttribute:NSRTFTextDocumentType], documentAttributes: nil)

all the other code same as Swift 4.x & 5.x.

For more details please read the Apple document related to the NSAttributedStringDocumentType

Answer 3

For HTML string, NSAttributedString.DocumentType.html is the correct option.

Swift 4

extension String {

    var utfData: Data? {
        return self.data(using: .utf8)
    }

    var htmlAttributedString: NSAttributedString? {
        guard let data = self.utfData else {
            return nil
        }
        do {
            return try NSAttributedString(data: data,
           options: [
                     NSAttributedString.documentType: NSAttributedString.DocumentType.html,
                     NSAttributedString.characterEncoding: String.Encoding.utf8.rawValue
                    ], documentAttributes: nil)
        } catch {
            print(error.localizedDescription)
            return nil
        }
    }
}

Answer 4

This works for me:

let attrStr = try! NSAttributedString(
    data: modifiedFont.data(using: .unicode, allowLossyConversion: true)!,
    options:[.documentType: NSAttributedString.DocumentType.html,
    .characterEncoding: String.Encoding.utf8.rawValue],
    documentAttributes: nil)

If you don’t add

.characterEncoding: String.Encoding.utf8.rawValue

the app will crash.

Answer 5

Had this after automatic conversion to Swift 4. Was fixed by changing from:

NSMutableAttributedString(data: data, 
   options: [NSAttributedString.DocumentAttributeKey.documentType : NSAttributedString.DocumentType.html], 
   documentAttributes: nil)

to:

NSMutableAttributedString(data: data,
   options: [.documentType : NSAttributedString.DocumentType.html],
   documentAttributes: nil) {

Answer 6

You need to pass one of the available NSAttributedString DocumentType options:

---

Hypertext Markup Language (HTML) document.

static let html: NSAttributedString.DocumentType

---

Plain text document.

static let plain: NSAttributedString.DocumentType

---

Rich text format document.

static let rtf: NSAttributedString.DocumentType

---

Rich text format with attachments document.

static let rtfd: NSAttributedString.DocumentType

---

In this case you will need to pass the first one (html) NSAttributedString.DocumentType.html

So the extension updated to Swift 4 should look like this:

extension NSAttributedString {
    convenience init(data: Data, documentType: DocumentType, encoding: String.Encoding = .utf8) throws {
        try self.init(data: data,
                      options: [.documentType: documentType,
                                .characterEncoding: encoding.rawValue],
                      documentAttributes: nil)
    }
    convenience init(html data: Data) throws {
        try self.init(data: data, documentType: .html)
    }
    convenience init(txt data: Data) throws {
        try self.init(data: data, documentType: .plain)
    }
    convenience init(rtf data: Data) throws {
        try self.init(data: data, documentType: .rtf)
    }
    convenience init(rtfd data: Data) throws {
        try self.init(data: data, documentType: .rtfd)
    }
}

---

extension StringProtocol {
    var data: Data { return Data(utf8) }
    var htmlToAttributedString: NSAttributedString? {
        do {
            return try .init(html: data)
        } catch {
            print("html error:", error)
            return nil
        }
    }
    var htmlDataToString: String? {
        return htmlToAttributedString?.string
    }
}

---

extension Data {
    var htmlToAttributedString: NSAttributedString? {
        do {
            return try .init(html: self)
        } catch {
            print("html error:", error)
            return nil
        }

    }
}

---

Playground Testing

let htmlString = "<style type=\"text/css\">#red{color:#F00}#green{color:#0F0}#blue{color: #00F; font-weight: Bold; font-size: 32}</style><span id=\"red\" >Red</span><span id=\"green\" > Green </span><span id=\"blue\">Blue</span>"

let htmlData = Data(htmlString.utf8)

htmlString.htmlToAttributedString
htmlData.htmlToAttributedString

Discussion The HTML importer should not be called from a background thread (that is, the options dictionary includes documentType with a value of html). It will try to synchronize with the main thread, fail, and time out. Calling it from the main thread works (but can still time out if the HTML contains references to external resources, which should be avoided at all costs). The HTML import mechanism is meant for implementing something like markdown (that is, text styles, colors, and so on), not for general HTML import