Re: copying a vector of objects at runtime

From:

red floyd <no.spam.here@example.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 10 Jul 2008 22:38:07 -0700

Message-ID:

<qiCdk.12091$cW3.7840@nlpi064.nbdc.sbc.com>

Joe Greer wrote:

"Julian" <julvar@nospamtamu.edu> wrote in
news:g54akk$c32$1@news.tamu.edu:

Hi,
I have a vector defined like this:
std::vector<Load*> LoadList;
which is populated with different objects of classes that are derived
from 'Load'.
I need to make a copy of this list during runtime.
I imagine I'd have to loop through the list, make a copy of each of
the objects in the vector using the copy constructor... but I don't
know the class name during run time so that I can call the appropriate
copy constructor.

Hmmm, if copying the objects in the vector is the answer, then I have to
wonder why there are pointers in the vector to begin with. That is,
wouldn't vector<Load> have been a better place to start? Then copying
would be as simple as LoadList2 = LoadList. IME the only time you
really want a vector of pointers is if the objects have identity
(can't/shouldn't be copied at all) or are horrendously expensive to
copy.

You forgot the other case, where your vector contains polymorphic
objects. But then you should probably be using a container of your
favorite smart pointer.