Re: Should I use pointer inside container?

From:
=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <Erik-wikstrom@telia.com>
Newsgroups:
comp.lang.c++
Date:
Mon, 10 Sep 2007 12:42:56 GMT
Message-ID:
<kZaFi.8339$ZA.4348@newsb.telia.net>
On 2007-09-10 14:16, terminator wrote:

On Sep 9, 3:23 pm, Erik Wikstr?m <Erik-wikst...@telia.com> wrote:

On 2007-09-09 13:34, terminator wrote:

On Sep 8, 5:27 pm, Erik Wikstr?m <Erik-wikst...@telia.com> wrote:

On 2007-09-08 16:04, Goran wrote:

Hi @ all!

Again one small question due to my shakiness of what to use...

What is better / smarter?

private:
    vector<MyClass_t> * itsVector;

OR...

private:
    vector<MyClass_t * > * itsVector;


None of the above, use either

   std::vector<MyClass> itsVector;

or

   std::vector<MyClass*> itsVector;

Which one you should use depends on how you will use the elements, if
you have not special needs the first one is generally preferable since
it removes the need to new and delete the elements manually.

There might be a few legitimate situations where you might need a
pointer to a vector, but I would say that it is most often a sign of bad
design.

How works such a stl container? Does it use heap or stack?


The elements contained in the vector are stored on the heap, notice
thought that for some containers, std::vector among them, the elements
might be re-located when you perform some operations on the containers,
so taking the address of an object can be hazardous.

In fact, I would say that when you find yourself using a pointer ask
yourself if you really need it. In most cases allocating on the stack or
using a reference is just as good.

--
Erik Wikstr?m


I tend to consider containers as very huge objects(due to the
unpredictable number of elements),and as far as I have been digging
into my platform`s library neither of STL containers are built upon
the idea of reference counting .I simply conclude that a pointer to a
container is not really that bad.As a rookie I must respect a pro but
I do not see any reason to complaign about 'vector <T> *' as you did.


In short use only pointers where ownership, lifetime, or efficiency
requires it, because it complicates the code.


thats exacltly the point,when you need to share a container in
different places, or very simpler the return of a function(this one
mabye bad design).


If the container is a member of the class using a reference would
probably be better.

--
Erik Wikstr?m

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