Modifying part of interface in C++

Asked Dec 18 '21 at 16:53

Active Dec 18 '21 at 16:53

Viewed 57 times

Say I have an interface I:

class I
{
public:
    virtual int f() = 0;
};

and class B implementing I:

class B: public I
{
public:
    int f() override { return 1; }
    ...
}

can I define a (template) class C so that:

class C implements I.
class C implements everything else B has without writing a wrapper for every B function.
class C overrides f().
underlying B instance uses unmodified B::f().

asked Dec 18 '21 at 16:53

Stepan Andreenko

1

sounds like `class C : public B { int f() override; };` – Marek R Dec 18 '21 at 16:58
This will completely override f() for the instance of B as well. – Stepan Andreenko Dec 18 '21 at 17:01
I don't follow your last bullet point. Under what circumstances would you expect to be able to invoke the "underlying B instance" and have it use `B::f`? – Nathan Pierson Dec 18 '21 at 17:04
Say I have B::g() that calls f(). I want it to use B::f(), not C::f(). – Stepan Andreenko Dec 18 '21 at 17:08
1

Try explicitly calling B::f() or this->B::f() in B – Sebastian Dec 18 '21 at 17:09
For me question suffers from [XY problem](https://xyproblem.info/). Please [edit] question and improve it. – Marek R Dec 18 '21 at 17:25
Ok, I need to transparently modify a stream without knowing full features of it. Does it help? – Stepan Andreenko Dec 18 '21 at 17:53
the solution in my comment should work, cf. also https://stackoverflow.com/questions/672373/can-i-call-a-base-classs-virtual-function-if-im-overriding-it – Sebastian Dec 18 '21 at 20:27

0 Answers0