重载 << 运算符时如何解决此错误消息

Question

when I try to overload the << operator I get the error "too many parameters for this operator function"?

This is the code I have written:

class studentrecord{
string firstname, lastname, grade;        
studentrecord(string firstname, string lastname, string grade){
    this -> firstname = firstname;
    this -> lastname = lastname;
    this -> grade = grade;
}

ostream& operator<<(ostream& os, const studentrecord& studentrecord) {
    os << "\n\t" << studentrecord.firstname << "\t" << studentrecord.lastname << "\t" << studentrecord.grade;
    return os;
}
};

Thanks for the help!

Answer 1

@DesmondGold pointed out the answer, just use the "friend" keyword.

The proper use of this function can be seen on this page:

Overloading the << Operator for Your Own Classes

The code becomes:

class studentrecord{
string firstname, lastname, grade;        
studentrecord(string firstname, string lastname, string grade){
    this -> firstname = firstname;
    this -> lastname = lastname;
    this -> grade = grade;
}

friend ostream& operator<<(ostream& os, const studentrecord& studentrecord) {
    os << "\n\t" << studentrecord.firstname << "\t" << studentrecord.lastname << "\t" << studentrecord.grade;
    return os;
}
};