NSAttributedString设置字体大小-swift

所以我试着让下面的代码起作用

return try NSAttributedString(data: data, attributes:[ NSFontAttributeName: UIFont(name: "Chalkduster", size: 18.0) ], options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding:String.Encoding.utf8.rawValue], documentAttributes: nil)

我也试过以下几种方法，但都失败了

extension String {
    var htmlToAttributedString: NSAttributedString? {

        guard let data = data(using: .utf8) else { return NSAttributedString() }
        do {
               let font = UIFont.systemFont(ofSize: 72)
               let attributes = [NSAttributedString.Key.font: font]
            return try NSAttributedString(data: data,  attributes: attributes, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding:String.Encoding.utf8.rawValue], documentAttributes: nil)
        } catch {
            return NSAttributedString()
        }
    }
    var htmlToString: String {
        return htmlToAttributedString?.string ?? ""
    }
}