Here are 2 classes
class B
{
private:
int x;
public:
friend std::istream& operator>>(std::istream& in, B& obj)
{
in >> obj.x;
return in;
}
};
class D: public B
{
private:
int y;
public:
friend std::istream& operator>>(std::istream& in, D& obj)
{
//?
}
};
Is there any way that I can overload the >> operator in class D so it will be able to access the element x in B?
Based on what you appear to be trying to do, you could also do this:
class B
{
private:
int x;
public:
friend std::istream& operator>>(std::istream& in, B& obj)
{
in >> obj.x;
return in;
}
};
class D: public B
{
private:
int y;
public:
friend std::istream& operator>>(std::istream& in, D& obj)
{
B* cast = static_cast<B*>(&D); //create pointer to base class
in >> *B; //this calls the operator>> function of the base class
}
};
Although there are probably other reasons to make x protected instead of private anyway.
Is there any way that I coverload the >> operator in class D so he will be able to access the element x in B?
Don't make x private.
By making it private, you're explicitly saying that access to it is restricted to class B and its friends. And from your question, it seems that you don't want that.
If it were protected instead, you could access it as obj.x.
operator >> here is a friend of D, not a member functionx needs to be protected. Otherwise it is not accessible directly from D.
class B
{
protected:
int x;
Then you can do
class D: public B
{
private:
int y;
public:
friend std::istream& operator>>(std::istream& in, D& obj)
{
in >> obj.x;
return in;
}
};
x is inherited by D in the sense that D has an x data member. It is just not accessible.
xprotected ;)