var str_trim = " !hi !23 !"
str_trim.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet())//"!hi !23 !"去掉兩邊的空格
str_trim.stringByTrimmingCharactersInSet(NSCharacterSet(charactersInString: "! "))//"hi !23" 去掉兩邊的空格和‘!’ ,把 字符串中的每個字符進行了分解並去除