       guard let range = span(index) where range.startIndex < string.endIndex else {
         return nil
       }
-      return string.substringWithRange(range)
+      return string[range]
     }
     
     /**

        self.regex = try NSRegularExpression(pattern: pattern, options: flags)
      } catch let error as NSError {
        self.regex = nil
        print(error)
      }
    }
    

    
    /// NSRegularExpressionOptions used to contructor this RegexObject
    public var flags: Flag {
      return regex?.options ?? []
    }
    
    /// Number of capturing groups
