HTML character decoding in Objective-C / Cocoa Touch

Question

First of all, I found this: Objective C HTML escape/unescape, but it doesn\'t work for me.

My encoded characters (come from a RSS feed, btw) look like this: &a

Answer 1

Here's a Swift version of Walty Yeung's answer:

extension String {
    static private let mappings = [""" : "\"","&" : "&", "<" : "<", ">" : ">"," " : " ","¡" : "¡","¢" : "¢","£" : " £","¤" : "¤","¥" : "¥","¦" : "¦","§" : "§","¨" : "¨","©" : "©","ª" : " ª","«" : "«","¬" : "¬","®" : "®","¯" : "¯","°" : "°","±" : "±","² " : "²","³" : "³","´" : "´","µ" : "µ","¶" : "¶","·" : "·","¸" : "¸","¹" : "¹","º" : "º","»" : "»&","frac14" : "¼","½" : "½","¾" : "¾","¿" : "¿","×" : "×","÷" : "÷","Ð" : "Ð","ð" : "ð","Þ" : "Þ","þ" : "þ","Æ" : "Æ","æ" : "æ","&OElig" : "Œ","&oelig" : "œ","Å" : "Å","Ø" : "Ø","Ç" : "Ç","ç" : "ç","ß" : "ß","Ñ" : "Ñ","ñ":"ñ",]

    func stringByDecodingXMLEntities() -> String {

        guard let _ = self.rangeOfString("&", options: [.LiteralSearch]) else {
            return self
        }

        var result = ""

        let scanner = NSScanner(string: self)
        scanner.charactersToBeSkipped = nil

        let boundaryCharacterSet = NSCharacterSet(charactersInString: " \t\n\r;")

        repeat {
            var nonEntityString: NSString? = nil

            if scanner.scanUpToString("&", intoString: &nonEntityString) {
                if let s = nonEntityString as? String {
                    result.appendContentsOf(s)
                }
            }

            if scanner.atEnd {
                break
            }

            var didBreak = false
            for (k,v) in String.mappings {
                if scanner.scanString(k, intoString: nil) {
                    result.appendContentsOf(v)
                    didBreak = true
                    break
                }
            }

            if !didBreak {

                if scanner.scanString("&#", intoString: nil) {

                    var gotNumber = false
                    var charCodeUInt: UInt32 = 0
                    var charCodeInt: Int32 = -1
                    var xForHex: NSString? = nil

                    if scanner.scanString("x", intoString: &xForHex) {
                        gotNumber = scanner.scanHexInt(&charCodeUInt)
                    }
                    else {
                        gotNumber = scanner.scanInt(&charCodeInt)
                    }

                    if gotNumber {
                        let newChar = String(format: "%C", (charCodeInt > -1) ? charCodeInt : charCodeUInt)
                        result.appendContentsOf(newChar)
                        scanner.scanString(";", intoString: nil)
                    }
                    else {
                        var unknownEntity: NSString? = nil
                        scanner.scanUpToCharactersFromSet(boundaryCharacterSet, intoString: &unknownEntity)
                        let h = xForHex ?? ""
                        let u = unknownEntity ?? ""
                        result.appendContentsOf("&#\(h)\(u)")
                    }
                }
                else {
                    scanner.scanString("&", intoString: nil)
                    result.appendContentsOf("&")
                }
            }

        } while (!scanner.atEnd)

        return result
    }
}