NSAttributedString Swift 4 [duplicate] - ios

Question

I found this string extension somewhere on SO 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?

Answer 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 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

Answer 2

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 3

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 4

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 5

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 6

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

Answer 7

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)

Answer 8

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