I have the following classes in C++:
class Event {
//...
friend ofstream& operator<<(ofstream& ofs, Event& e);
};
class SSHDFailureEvent: public Event {
//...
friend ofstream& operator<<(ofstream& ofs, SSHDFailureEvent& e);
};
The code I want to execute is:
main() {
Event *e = new SSHDFailureEvent();
ofstream ofs("file");
ofs << *e;
}
This is a simplification, but what I want to do is write into a file several type of Events in a file. However, instead of using the operator << of SSHDFailureEvent, it uses the operator << of Event. Is there any way to avoid this behavior?
Thanks
That would not work, as that would call operator<<
for the base class.
You can define a virtual function print
in base class and re-define it all derived class, and define operator<<
only once as,
class Event {
virtual ofstream& print(ofstream & ofs) = 0 ; //pure virtual
friend ofstream& operator<<(ofstream& ofs, Event& e);
};
//define only once - no definition for derived classes!
ofstream& operator<<(ofstream& ofs, Event& e)
{
return e.print(ofs); //call the virtual function whose job is printing!
}