Re: Deriving from concrete types

From:

Ulrich Eckhardt <eckhardt@satorlaser.com>

Newsgroups:

comp.lang.c++.moderated

Date:

28 Jun 2006 06:32:21 -0400

Message-ID:

<d1n7n3-131.ln1@satorlaser.homedns.org>

Alan McKenney wrote:

Kirit S?lensminde wrote:

class MyVector : private std::vector< int > {
public:
     using operator [];
     using resize;
     // etc.
};

Now you can control exactly the members that you wish to include and
you cannot use a MyVector as a substitute for any std::vector< int >
either.

True.

But if you want all the std::vector<> member functions, how is this
better than just using public inheritance?

The point is that now you have exact control. In particular, access to the
base-class' destructor is denied, which would lead to UB if it was used.

A disadvantage of putting in "using" declarations for every
std::vector function is that it's an opportunity for errors and
omissions.

Omissions, yes, errors less so. The worst that can happen is a compiler
error because you forgot to allow access to a functions. In the case of
public inheritance, the worst that can happen is undefined behaviour. I
prefer compile-time errors by far.

Uli

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