[postStrstringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSetURLQueryAllowedCharacterSet]]
转回去
[strstringByRemovingPercentEncoding]
[postStrstringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSetURLQueryAllowedCharacterSet]]
转回去
[strstringByRemovingPercentEncoding]