错误：没有匹配函数来调用＆＃39; std :: strstream :: str（std :: string）＆＃39;

Question

我试图使用stream.str清除std :: strstream（＆＃34;＆＃34;）（How do you clear a stringstream variable?）但是我得到了：

error: no matching function for call to 'std::strstream::str(std::string)'
note: candidate is:
note: char* std::strstream::str()

im includeing：#include <strstream>