增加了 # 符号，使得写字符串更加简单。

• 在字符串中包含 " 时不必再加 \

    //before
   let rain = "The is\"new\"string" 
    //after
    let rain = #"The is"new"string"#
  

• 包含 \ 反斜杠也不需要再加转义符

     //before
    let rain = "The is\\new string" 
    //after
    let rain = #"The is \new string"#
  

• 由于反斜杠作为字符串中的字符，所以在插入值的时候需要在后面再加个 #

•     //before
     let age = 26
     let dontpanic = "myAge is \(age)"
     // after
     let answer = 26
     let dontpanic = #"myAge is \#(age)"#
  

  *当字符串包含 # 时， 前后应用 ## 包裹字符串

     let str = ##"this is "a"#good ideal"##   
  

*用 #""" 开头 """#结尾 来表示多行字符串

  let multiline = #"""
  The answer to life,
  the universe,
  and everything is \#(answer).
  """#

• 由于不用反斜杠转义 使得正则表达式更加简洁明了

     //before
     let regex1 = "\\\\[A-Z]+[A-Za-z]+\\.[a-z]+"
    //after
     let regex2 = #"\\[A-Z]+[A-Za-z]+\.[a-z]+"#