CODEWITHSUNDEEP
c++variablesinheritanceprivate
K. Jessergrim
K. Jessergrim

Reputation: 11

C++ private variable names and inheritance ambiguities

This is about C++ (not java) inheritance and ambiguities in variable names.

Suppose that I am in this situation:

class A{
public:
void fct(){do something with x;}

private:
int x;
};

class B: public A{
private:
int x;
};

If I define some instance of the derived class

B foo;

and then call

foo.fct();

will fct() act on A::x or B::x? I would like it to be acting on A::x. I wonder whether declaring x as private in class A is enough to make it safe against non-wanted ambiguities which may arise when defining derived classes.

I understand that just using a different name for B::x would be the best thing to do... but suppose that one is "distracted" and forgets that the private A::x exists, how bad the consequences would be?

Thank you!

Upvotes: 1

Views: 153

Answers (2)

SergeyA
SergeyA

Reputation: 62613

Since fct is non-virtual, it will always deal with x as a member of it's own class. It won't know anything about any other xs in any other classess.

However, if fct were to declared virtual and overridden in the child class, child override it would be called instead - and this one could be programmed so that it would use other x.

Upvotes: 3

Sean
Sean

Reputation: 62532

Calling fct will act on A::x. The fact that derived classes have member variables with the same name is irrelevant since the member is private and hidden from them.

If it were able to see B::x then that would be a bit like having virtual data!

Upvotes: 1

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