错误:无法将'std::ostream {aka std::basic_ostream<char>}‘lvalue绑定到'std::basic_ostream<char>&&’

Question

因此，我最近在c++大学期间批准了OOP，我发现自己遇到了一些问题。我尝试超载ostream operator <<，并发现自己有一些问题要解决。首先，像ostream& operator<<(ostream& outs, const Test&);那样执行重载带来了一个被描述为\src\Test.h:15:48: error: 'std::ostream& test::Test::operator<<(std::ostream&, const test::Test&)' must take exactly one argument ostream& operator<<(ostream& outs, const Test&);的问题，所以，就像我对operator ==做的一样，删除了第二个参数。但是，一旦我尝试构建以下代码，我就会得到错误：\src\main.cpp:9:10: error: cannot bind 'std::ostream {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&' cout << t;。我读过这个错误，但不能把它加起来，我应该做什么，我在做什么错误？

Test.h

#include <iostream>
#include <cstring>
using namespace std;
#ifndef SRC_TEST_H_BECCIO
#define SRC_TEST_H_BECCIO

namespace test {

class Test {
private:
    string mStr;
public:
    Test(string str);
    string getString(){return this->mStr;};
    ostream& operator<<(ostream& outs);
};

} /* namespace test */

#endif /* SRC_TEST_H_BECCIO */

Test.cpp

#include "Test.h"

namespace test {

Test::Test(string str) {
    this->mStr=str;

}

ostream& Test::operator<<(ostream& outs){

    outs << this->getString()<<endl;
    return outs;
}

} /* namespace test */

main.cpp

#include <iostream>
#include "Test.h"
using namespace std;
using namespace test;

int main() {

    Test t("let's hope this goes well");
    cout << t;
    return 0;
}

Answer 1

看起来论点的顺序是倒的。见https://learn.microsoft.com/en-us/cpp/standard-library/overloading-the-output-operator-for-your-own-classes。尝试这个声明，以及类似的实现：

friend ostream& operator<<(ostream& os, Test t);