ostream method does not work - c++

Question

i have two methods the first one defined string:
I do not understand why it does not make it and how i call to this method from the main.
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;
}
the next one need to print it
const Actor& Actor::print(std::ostream& os) {
os<< std::string();
return *this;
}

Answer 1

Is not clear why your doing this because the normal way to work is overloading ostream operator:
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;
}
};
In this way, from main, you can create and print actor easily:
Actor a;
cout << a;
First method
Actor::operator std::string() const();
allow you implicit conversion from Actor to string, for example:
Person a;
std::string s = a;

Answer 2

os<< std::string();
This does not call the conversion to string, it creates a temporary string variable and writes it to the stream, so it is equivalent to:
os << "";
To call the conversion operator you need to tell the compiler you want to convert the object to a string (not just construct an empty string). The explicit way to do that is:
os << static_cast<std::string>(*this);
There are other ways such as:
os << std::string(*this);
os << (std::string)*this;
std::string s = *this;
os << s;
or if you like unreadable code you can call the conversion operator explicitly:
os << this->operator std::string();
(That last way is not a good idea.)
The definition of your conversion operator is very silly, and much slower than it needs to be. Using two separate stringstreams and also string concatenation is very wasteful, you can do it all with a single stringstream:
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();
}
However, as Velthune says, unless you need conversion to string for other reasons, the usual way to output your class would be to overload operator<< for the class.