C++ ostream方法不起作用

我有两个方法，第一个是定义的字符串：

我不明白为什么它不能成功，以及我如何从main调用这个方法

Actor::operator std::string( ) const {
    std::stringstream ss;
    ss << this->_id;
    std::string str1 = ss.str();

    std::stringstream s;
    s << this->_salary;
    std::string str2 = s.str();

    std::string str3 = "Actor first name = " + this->_firstname + ", last name = " + this->_lastname+", id = " + str1 + ", monthly salary = " + str2;
    if (this->_hasoscar==true)
        str3+=" was NOMINATED Oscar AWARD..";

    return str3;
}

下一个需要打印出来

const Actor& Actor::print(std::ostream& os) {
    os<< std::string();
    return *this;
}

---

不清楚为什么要这样做，因为正常的工作方式是重载ostream运算符：

class Actor  {
public:
  friend std::ostream& operator<< (std::ostream& os, const Actor& a) {
    os << "Actor first name = " + a._firstname + 
          ", last name = " + a._lastname+", id = " + 
          a._id + ", monthly salary = " + a._salary;
    if (this->_hasoscar) {
       os << " was NOMINATED Oscar AWARD.."; 
    } 
    return os;
  }
};

允许从参与者隐式转换为字符串，例如：

Person a;
std::string s = a;

---

你误用了，不要编译？问题出在哪里？它是编译的，但我不知道如何从main@GR这有什么关系吗@詹姆斯：这对我很重要。我不得不忍受，他们也要忍受！我不是这样称呼它的：a.print？@user3669000:不，这不是传统的做法。不过，这也不会错。如果像id和薪水这样的东西不是原始代码所指示的字符串（似乎使用stringstream来转换它们），可能需要将其拆分一下。

Actor::operator std::string() const();

Person a;
std::string s = a;

os << "";

os << static_cast<std::string>(*this);

os << std::string(*this);

os << (std::string)*this;

std::string s = *this;
os << s;

os << this->operator std::string();

Actor::operator std::string( ) const {
    std::stringstream ss;
    ss << "Actor first name = " << this->_firstname
       << ", last name = " << this->_lastname
       << ", id = " << this->_id
       << ", monthly salary = " << this->_salary;

    if (this->_hasoscar==true)
        ss << " was NOMINATED Oscar AWARD..";

    return ss.str();
}