c++ - 如何通过 stdstring 打印 ostream 变量的值？

Question

我尝试通过转换为字符串来打印 ostream 变量中存在的值，然后打印字符串而不是 ostream 参数。
但它不起作用。

这是我的代码:

#include <iostream>
#include <cassert>
#include <cstring>
#include <sstream>

using std::ostream;

typedef std::basic_stringstream<char> stringstream;
class X {
public:
    int y;
};

std::ostream& operator<<(std::ostream& os, const X x) {
    return os << x.y;
}

int main() {
    X x;
    x.y = 5;

    stringstream ss;
    ostream output(nullptr);
    output << x;
    ss << output.rdbuf();
    std::string myString = ss.str();

    std::cout << x << std::endl; // 5
    std::cout << "myString.c_str() :" << std::endl;
    std::cout << myString.c_str() << std::endl; // nothing.
}

我该如何解决这个问题，才能到达 myString.c_str()合适的输出？

std::cout << myString.c_str() << std::endl; 中的输出行是 ""(空字符串 - 什么都没有)，我希望它是 5也是(即 output 类型的 char* )..

Answer 1

引自 http://www.cplusplus.com/reference/fstream/ofstream/rdbuf/

std::ofstream::rdbuf

Returns a pointer to the internal filebuf object.

Notice however, that this is not necessarily the same as the currently associated stream buffer (returned by ios::rdbuf).