Re: Getting non "const" pointers to object data using "const" members

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 23 Mar 2009 14:37:51 -0400

Message-ID:

<OA0w$d#qJHA.5912@TK2MSFTNGP02.phx.gbl>

Gingko <Gingko@nospam.nospam> wrote:

"Igor Tandetnik" <itandetnik@mvps.org> a ?crit dans le message de
news:%23gELCC9qJHA.6116@TK2MSFTNGP03.phx.gbl...

Gingko <Gingko@nospam.nospam> wrote:

Of course, my actual programming is much more complex than that, and
removing the "const" attributes would also have the side effect of
removing the "const" protection for all OTHER members of the same
classes, thus loosing many of the advantages of using the "const"
attributes...

What are those advantages, considering that, if you have your way,
the object can be modified at any time by any piece of code in an
arbitrary manner that doesn't necessarily preserve object's
invariants?

Except one thing ...

The returned pointers are not arbitrary, they are *selected* parts of
the object, other parts are still expected to be not accessible.

Then mark those parts mutable, and you'll be able to return pointers to
them from const members.

But still, I'd provide a proper interface for these modificatons, rather
granting everyone direct access.

My object is actually a tree container, and the member function
explores all branches for returning a flattened list of pointers to
all leaves.

Const member should be able to do that. Constness is shallow:

class Node {
  Node* child;
  Node* getChild() const { return child; } // should compile
};

--
With best wishes,
    Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925