Swift – String Optional Extension

extension Optional where Wrapped == String {
    func nullable(nd:String)->String
    {
        if let n = self {
            return n
        }
        return nd
    }
    var nullable:String {
        get {
            if let n = self {
                return n
            }
            return " "
        }
    }
    var nullableDate:String {
        get {
            if let n = self {
                return n
            }
            return "2000-01-01 00:00:00"
        }
    }
    var nullableDateLong:String {
        get {
            if let n = self {
                return n
            }
            return "2000-01-01 00:00:00"
        }
    }
}