C++ - ostream (<<) overloading - c++

Question

I was wondering if there is any way to overload the << operator for a class without declaring it as a friend function. My professor said this is the only way to do it, but I wanted to know if there is another way that he was unaware of.

Answer 1

There is no need to make the operator<< function a friend of the class as long as everything you want to be output is accessible through the public interface of the class.

Answer 2

You need to declare it is as friend function if and only if you need access to it's private members.
You can always do this without using friend function if:
1) No private member access is required.
2) You provide a mechanism to access your private member otherwise. e.g.
class foo
{
int myValue;
public:
int getValue()
{
return myValue;
}
}

Answer 3

Yes, you can
std::ostream& operator<<(std::ostream &stream, WHATEVER_TYPE var) {
std::string str = somehowstringify(var);
return stream << str;
}
Note however that by virtue of it being a non-member non-friend function it can of course only access the public interface of std::ostream, this usually isn't a problem.

Answer 4

Yes, one way to do it is like this:
class Node
{
public:
// other parts of the class here
std::ostream& put(std::ostream& out) const { return out << n; };
private:
int n;
};
std::ostream& operator<<(std::ostream& out, const Node& node) {
return node.put(out);
}

Answer 5

As R Sahu has pointed out, the requirement is that the operator should be able to access everything it has to display.
Here are a few possible options
1.Adding the overloaded function as a friend function
2.Making all the required data members of the class accessible for the function using either public accessor methods or public data members
class MyClass {
private:
int a;
int b;
int c;
public:
MyClass(int x,int y,int z):a(x),b(y),c(z) {};
MyClass():a(0),b(0),c(0) {};
int geta() { return a; }
int getb() { return b; }
int getc() { return c; }
};
std::ostream& operator<<(std::ostream &ostr,MyClass &myclass) {
ostr << myclass.geta()<<" - " << myclass.getb() << " - " << myclass.getc() ;
return ostr;
}
int main (int argc, char const* argv[])
{
MyClass A(4,5,6);
cout << A <<endl;
return 0;
}
3.Add a public helper function , say output with the signature std::ostream& output(std::ostream& str) and use it later in the operator function.