iOS url出现特殊字符处理 -- stringByAddingPercentEncodingWithAllowedCharacters

stringByAddingPercentEscapesUsingEncoding(只对 `#%^{}[]|"<> 加空格共14个字符编码，不包括”&?”等符号), ios9将淘汰，建议用 stringByAddingPercentEncodingWithAllowedCharacters 方法

stringByAddingPercentEncodingWithAllowedCharacters  需要传一个  NSCharacterSet  对象（关于  NSCharacterSet 这篇 文章说的很好）

如[NSCharacterSet  URLQueryAllowedCharacterSet]

URLFragmentAllowedCharacterSet  "#%<>[]^`{|}

URLHostAllowedCharacterSet      "#%/<>?@^`{|}

URLPasswordAllowedCharacterSet  "#%/:<>?@[]^`{|}

URLPathAllowedCharacterSet      "#%;<>?[]^`{|}

URLQueryAllowedCharacterSet    "#%<>[]^`{|}

URLUserAllowedCharacterSet      "#%/:<>?@[]^`

（2）网络访问请求：中文空格字符解码

stringByRemovingPercentEncoding  ----  xcode7可能会提示要将stringByAddingPercentEscapesUsingEncoding替换成此方法，要根据是否是解码来区分

代替  stringByAddingPercentEscapesUsingEncoding

let customAllowedSet =  NSCharacterSet(charactersInString:"`#%^{}"[]|\<> ").invertedSet

NSString *urlStr = [urlStr stringByAddingPercentEncodingWithAllowedCharacters:[[NSCharacterSet characterSetWithCharactersInString:@"?!@#$^&%*+,:;='"`<>()[]{}/\| "] invertedSet]];