带有iOS 8的Swift 4

Question

更新我的代码后Swift4,应用程序在iOS 8.3上崩溃.我收到了以下错误

dyld:找不到符号:_NSCharacterEncodingDocumentOption引用自:/private/var/mobile/Containers/Bundle/Application/213D60CD-1ED9-4811-A3C7-B47383557453/development.app/development期望:/ System/Library/Frameworks/UIKit.框架/ UIKit的

  var decoded: String {

    let encodedData = self.data(using: String.Encoding.utf8)!
    let attributedOptions: [NSAttributedString.DocumentReadingOptionKey : Any] =
        [
           .documentType: NSAttributedString.DocumentType.html ,
           .characterEncoding: String.Encoding.utf8.rawValue
    ]

    do {
         let attributedString = try NSAttributedString(data: encodedData, options: attributedOptions, documentAttributes: nil)
         return attributedString.string
    } catch _ {

        return self

    }

}