Re: list of all objects in a templated class

From:
"Fred Zwarts" <F.Zwarts@KVI.nl>
Newsgroups:
comp.lang.c++
Date:
Thu, 9 Jul 2009 16:09:11 +0200
Message-ID:
<h34tm8$m3u$1@news.albasani.net>

"Ajay 0x007" <ajay.0x007@gmail.com> wrote in message =

news:2da11b82-0a91-4035-ac11-199f53f7a21f@f20g2000prn.googlegroups.com...=

On Jul 9, 3:52 pm, Alan Woodland <aj...@aber.ac.uk> wrote:

Ajay 0x007 wrote:

Hi,
I have a templated class and I want to mantain a list pointers of =

all

objects of that class. How it can be achieved???

If i do like below (make list as static member variable of same =

class)

then the list will be different for all typename X, i.e.

template <typename X> class A{
static std::vector<class<X>* > list;
A(){
list.push_back(this);
}
};

If I make a global pointer instead of static member variable as =

above

then I need to provide actual argumenst to X which I cannot know in
advance.

Is their any way to achiev that?


How about another class that all A's inherit from? You could store
pointers to them without any trouble... you could even add one or =

more

virtual methods to that class to do something useful with!

What's your motivation for doing this though? There might be other
solutions too.

Alan- Hide quoted text -

- Show quoted text -


base class mantaining the list of templated class is not possible, How
the template argument be determined in base class??? i.e.

class base {
   std::vector<class A<X>* > list;
};
class A:public base{
};
How the "X" in base class will be determined?


class base {
  std::vector <base *> list;
  base () {
    list.push_back (this);
  }
};

template <class x>
class A : public base {
};

This will create the list.

Using virtual functions in class base will remove the necessity the =
determine
the exact pointer types in the list. (Recommended method.)

If for some reason you need to access members in a derived class that =
are
not in base, type_info and/or dynamic_cast can be used to determine the
exact pointer type of the pointers in the list. (Not recommended.)

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