iOS中 UTF-8转码

    UTF-8转码 : 
    iOS 9.0以后 - 进行utf-8编码
NSString *utf8Str = [string stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
  解码:
NSString *str = [utf8Str stringByRemovingPercentEncoding];

  iOS 9.0之前 - 进行utf-8编码
NSString *utf8Str = [string stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
解码:
NSString *str = [utf8Str stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];