Re: A little confused with this (const ptrs)

From:

"mlimber" <mlimber@gmail.com>

Newsgroups:

comp.lang.c++

Date:

15 May 2006 08:25:51 -0700

Message-ID:

<1147706751.245227.180510@u72g2000cwu.googlegroups.com>

Bit byte wrote:

I want to have a class that contains an object (actually a structure) -
lets call it data type A. I want the container class to have a method
which allows it to accept a new variable of data type A, and then
replaces its previous variable of data type A with the newly received one.

This same class, will receive requests by other classes, who want to use
the object. However, I do not want any class receiving this
class/structure, to be able to modify (and certainly not delete) the
received object.

This is the problem I'm trying to solve. Any pointers (no pun intended)
wll be much appreciated.

A few solutions spring to mind: (1) use a reference instead of a
pointer, as Rolf suggested, since that would make it less likely (but
not impossible!) that the user would try to delete the object. (2) Use
std::tr1::shared_ptr (aka boost::shared_ptr), with which the user is
relieved of deleting the object anyway and should not try to do so. (3)
Return some other proxy object that has no public interface but is
accessible to specific friends via the attorney-client idiom (cf.
http://www.ddj.com/showArticle.jhtml?articleID=184402053).

Note that you're trying to prevent the user from making mistakes.
That's good. However, you can't prevent the user from doing all sorts
of evil if s/he refuses to be civil about things.

Cheers! --M