NSCharacterSet常用的类型有以下：
urlHostAllowed "#%/<>?@\^`{|}
urlFragmentAllowed "#%<>[\]^`{|}
urlPasswordAllowed "#%/:<>?@[\]^`{|}
urlPathAllowed "#%;<>?[\]^`{|}
urlQueryAllowed "#%<>[\]^`{|}
urlUserAllowed "#%/:<>?@[\]^`
NSCharacterSet常用的类型有以下：
urlHostAllowed "#%/<>?@\^`{|}
urlFragmentAllowed "#%<>[\]^`{|}
urlPasswordAllowed "#%/:<>?@[\]^`{|}
urlPathAllowed "#%;<>?[\]^`{|}
urlQueryAllowed "#%<>[\]^`{|}
urlUserAllowed "#%/:<>?@[\]^`
