NSCharacterSet常用的类型有以下：
urlHostAllowed "#%/<>?@\^`{|}
urlFragmentAllowed "#%<>[\]^`{|}
urlPasswordAllowed "#%/:<>?@[\]^`{|}
urlPathAllowed "#%;<>?[\]^`{|}
urlQueryAllowed "#%<>[\]^`{|}
urlUserAllowed "#%/:<>?@[\]^`
原文链接：https://www.f2er.com/swift/321900.html