Re: What's wrong with this class

James Kanze <>
Sat, 25 Oct 2008 01:53:53 -0700 (PDT)
On Oct 25, 12:00 am, Mosfet <> wrote:

James Kanze a =E9crit :

Actually I am reading effective STL and there is a chapter
where is written :
Containers will make a copy of the object that you insert.
This is fine when inserting integers and strings, but for
large/complex objects becomes undesirable. If you do not want
multiple copies of the object floating around, store pointers
in containers rather than actual objects. If you are happy
with multiple copies, get to know your copy-constructor.

Usually I use object and not pointers but I told me that I
could try with pointers. OF course there are some issues with
pointer ownerships so I will do as I always do and will do
some advanced tricks only in a few years ;-)

There is one idiom that might be applicable here: make the
contained objects immutable, and use boost::shared_ptr to manage
them. (Or better yet, develop your own invasive reference
counted pointer, based on e.g. the one in item 29 of "More
Effective C++".) This basically duplicates the way you'd handle
a value type in Java, with two restrictions: your value objects
can't contain pointers to other objects which might create
cycles, and it isn't thread safe. And it generally isn't worth
the bother, unless the objects are very, very expensive to copy
(not your case).

James Kanze (GABI Software)
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