问题:

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

func html2AttributedString() -> NSAttributedString {     return try! NSAttributedString(data: self.data(using: String.Encoding.unicode, allowLossyConversion: true)!, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) }

It worked fine in Swift 3, but with Swift 4, Xcode complains:

Cannot convert value of type 'NSAttributedString.DocumentAttributeKey' to expected dictionary key type 'NSAttributedString.DocumentReadingOptionKey'

How do I fix this?

回答1:

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

回答2:

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.

回答3:

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) {

回答4:

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         }     } }

回答5:

swift 4 : i dont know why but all answer have compiler error for me. so i use this extention:

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

回答6:

I use NSAttributedStringKey and had similar error "Cannot convert value of type" on Swift 4. In case anyone using NSAttributedStringKey comes here looking for an answer, this is how I fixed:

let TextStroke: [NSAttributedStringKey : Any] = [     NSAttributedStringKey(rawValue: NSAttributedStringKey.strokeColor.rawValue) : UIColor.black,     NSAttributedStringKey(rawValue: NSAttributedStringKey.foregroundColor.rawValue) : UIColor.white,     NSAttributedStringKey(rawValue: NSAttributedStringKey.strokeWidth.rawValue) : -6.0,]

And this is how I add the attribute to the text:

myLabel.attributedText = NSAttributedString(string: myString, attributes: TextStroke)

转载请标明出处:Cannot convert value of type NSAttributedString.DocumentAttributeKey to .DocumentReadingOptionKey

文章来源: Cannot convert value of type NSAttributedString.DocumentAttributeKey to .DocumentReadingOptionKey

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