Swift-based Data to String reversible ValueTransformer supporting different string encodings (allowing binding from NSData to NSTextField and back for example)

DataToStringReversableTransformer.swift

@objc class DataToStringReversableTransformer: ValueTransformer {
   static func RegisterTransformer() {
      ValueTransformer.setValueTransformer(
         DataToStringReversableTransformer(encoding: .utf8),
         forName: NSValueTransformerName("DataToStringReversableTransformer_utf8")
      )
      ValueTransformer.setValueTransformer(
         DataToStringReversableTransformer(encoding: .utf16),
         forName: NSValueTransformerName("DataToStringReversableTransformer_utf16")
      )
   }

   let encoding: String.Encoding

   init(encoding: String.Encoding) {
      self.encoding = encoding
      super.init()
   }

   override class func transformedValueClass() -> AnyClass {
      return NSString.self
   }

   override class func allowsReverseTransformation() -> Bool {
      return true
   }

   override func transformedValue(_ value: Any?) -> Any? {
      if let v = value as? Data {
         return String(data: v, encoding: self.encoding)
      }
      return nil
   }

   override func reverseTransformedValue(_ value: Any?) -> Any? {
      if let v = value as? String {
         return v.data(using: self.encoding)
      }
      return nil
   }
}