Calling Overloaded Oper from an inherited class!
Author
In c++ oop, Is there a way to call a an overloaded << friend function in a base class from a derived class? I read somewhere that friend functions from a base class isnt inherited so in order to use them they have to be called from a inherited class? Any idea on how this would work? Heres an example, let's say I had a class Pet, and a class Dog inherited from class pet. Inside my class Pet i have an overloaded << friend function that outputs lets say the pets name or something, how would i use that same function in class Dog? Thanks for the time
MasterDario
If I understand you set up correctly, you should be able to use the scope-resolution operator ('::') to call the function from the derived class. So, going off your Dog / Pet example:
void Dog::CallBase(){ Pet::operator<<(/* arguments here */);}
Have the overloaded << function call a private virtual function in pet to get the information required. Then override that function in dog.
#include <iostream>#include <string>class pet{public: friend std::ostream& operator << (std::ostream& os, pet& p) { os << p.whatAmI(); return os; } virtual ~pet(){}private: virtual std::string whatAmI()const { return "I am a pet"; }};class dog : public pet{private: virtual std::string whatAmI()const { return "I am a dog"; }};int main(){ dog aDog; std::cout << aDog;}
Author
thats what i figured, but the problem is that my overloaded << function is a friend function so its not really a member of my base class.
Hmmm ... woulda thought you could access the friend function that way. In that case go with Nitage's suggestion.
Author
hmm is there a way to do it without virtual functions though because i don't know much about them yet. Like i tried overloading the operator << without making it a friend function but if i do it that way it wont allow more than one paramater.
You can try declaring a member function in the base that forwards the call to the overloaded operator. Then you could call that function from the derived class.
Something like this:
Something like this:
class Pet{ public: friend std::ostream& operator<<(std::ostream& os, Pet& p) { /* Do whatever */ return os; } // Member function just calls the << operator with itself // as the argument. std::ostream& CallStreamOperator(std::ostream& os) { return (os << *this); }};class Dog{ public: std::ostream&CallStreamOperator(std::ostream& os) { /* Do whatever with os here */ return Pet::CallStreamOperator(os); }};This topic is closed to new replies.
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