how to display class data members stored in multimap - c++

Question

here is the code
class student
{
int num;
string name;
float marks;
public:
void add()
{
cout << "Enter the num name and marks:" << endl;
cin >> num >> name >> marks;
}
void display()
{
cout << num << endl;
cout << name << endl;
cout << marks << endl;
}
};
void main()
{
student ss;
multimap<int,student> st;
multimap<int,student>::iterator itr;
ss.add();
st.insert(make_pair(1000, ss));
for (itr = st.begin(); itr != st.end(); itr++)
{
cout << itr->second; // its showing ERROR
}
}
the error is
Error C2679 binary '<<': no operator found which takes a right-hand operand of type 'student' (or there is no acceptable conversion) firstmultimap
how to fix this

Answer 1

To display the student object you need to overload << operator.
I have made the operator overloading function friend of student class so it could be called without creating an object.
Also, check this example on MSDN.
Example:
#include<iostream>
#include<map>
#include<string>
using namespace std;
class student
{
private:
int num;
string name;
float marks;
public:
void add()
{
cout << "Enter the num name and marks:" << endl;
cin >> num >> name >> marks;
}
void display()
{
cout << num << endl;
cout << name << endl;
cout << marks << endl;
}
friend ostream &operator << (ostream &output, const student &s)
{
output << "Num: " << s.num << "\nName: " << s.name << "\nMarks: " << s.marks << endl;
return output;
}
};
int main()
{
student ss;
multimap<int, student> st;
multimap<int, student>::iterator itr;
ss.add();
st.insert(make_pair(1000, ss));
for (itr = st.begin(); itr != st.end(); itr++)
{
cout << itr->second;
}
// Using Range based for loop
// for(const auto &i : st)
// cout << i.second;
return 0;
}