CODEWITHSUNDEEP
c++virtual-functions
athos
athos

Reputation: 6425

How to prevent a derived class object under base class pointer calling a public nonvirtual function defined in base class but overridden in derived?

Suppose base class B has a nonvirtual public function f() , which is unfortunately overridden by derived class D.

Then there's a D object d passed to a B pointer pB.

Is there a way to prevent calling pB->f()?

Upvotes: 0

Views: 104

Answers (2)

Useless
Useless

Reputation: 67812

If you can change B, you can either make f virtual, or make it forward to a virtual protected do_f, or various other things.

If you can't change B, you can't stop it's public method being called, and you can't somehow intercept a call to a non-virtual base class method.

Upvotes: 1

Davislor
Davislor

Reputation: 15154

Your question essentially asks, “How do I make a function virtual?” You don’t give a reason why you can’t just do that, but maybe you can’t change the declaration of B.

If B has at least one virtual function, you could use RTTI to check if *pB is really a D and cast it to D& if so. You cannot make existing code that takes a B* do so; if your daughter class breaks when you call it as a B, it breaks the contract of that interface.

Otherwise, it might be possible to determine that *pB is a D somehow by calling the B interface, but that would be some rigmarole specific to B and D.

Upvotes: 0

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