Re: Is finalizing a virtual method possible in C++?

From:

Kira Yamato <kirakun@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Fri, 22 Feb 2008 08:29:42 -0500

Message-ID:

<2008022208294216807-kirakun@earthlinknet>

On 2008-02-22 08:05:28 -0500, "Alf P. Steinbach" <alfps@start.no> said:

* Kira Yamato:

On 2008-02-22 07:35:34 -0500, Pavel Lepin <p.lepin@ctncorp.com> said:

Kira Yamato <kirakun@earthlink.net> wrote in
<2008022206570016807-kirakun@earthlinknet>:

So, I don't want to say too hestantly that it is
impossible to simulate the finalizing of virtual methods
and classes in C++.

Hence, I rather turn to the experts and ask if anyone
knows if it is possible to simulate them in any way?

This is a FAQ.

<http://www.parashift.com/c++-faq-lite/>

Yes. Thanks. But the FAQ does not say that finalizing method is
impossible. If in fact it did, then the answer is found. Instead, it
just proposes a "solution."

So let me try asking differently, has anyone gotten further with a
better solution than merely stating a comment?

There should be no reason to finalize a member function in C++.

But if you absolutely must it's not that difficult.

     class Base
     {
     friend class Derived;
     private:
         struct OverrideTag {};
     public:
         virtual void foo( OverrideTag = OverrideTag() ) = 0;
     };

     class Derived: public Base
     {
     public:
         virtual void foo( OverrideTag = OverrideTag() ) {}
     };

     class FurtherDerived: public Derived
     {
     public:
         // Nix njet.
     // virtual void foo( OverrideTag = OverrideTag() ) {}
     };

Neat. So, it uses a similar trick as the final class method. You
should email the owner of the C++ FAQ and propose this as another
possible solution.

[...]
However, chances are that if you do something like this then you're
thinking in Java, not in C++, using ideas that don't make sense in C++.

I'm not disagreeing with you here, but I like to hear the reason why
you feel that this is not necessary (or maybe even wrong) in C++ to
finalize methods.

--

// kira