Streams
Overloading << Operator For ostream
A common and useful practise is to overload the <<
operator for an ostream
on your own classes. This allows you to then write things such as:
MyClass myClass;
std::cout << "My class = " << myClass << std::endl;
One way to do this is to overload the operator from within your class header file, declaring std::ostream
as a friend:
#include <sstream>
class MyClass {
public:
friend std::ostream& operator<<(std::ostream &out, const MyClass& rhs);
private:
int myVar_;
};
And then the definition in the .cpp
would look like:
std::ostream &operator<<(std::ostream &out, const MyClass& rhs) {
out << "{ ";
out << std::to_string(myVar_);
out << " }";
return out;
}
A Generic Overload For All Classes
Since C++11, you can make a generic overload that will work for all classes that contain a public method called Print(std::ostream&)const
.
template<class T>
auto operator<<(std::ostream& os, const T& t) -> decltype(t.Print(os), os) {
t.Print(os);
return os;
}
This saves you to work of having to overload the <<
operator for each class you design!