Re: Generic object with a member whose type is the iterator type of its container

From:

cbarron3@ix.netcom.com (Carl Barron)

Newsgroups:

comp.lang.c++.moderated

Date:

3 Jul 2006 07:13:34 -0400

Message-ID:

<1hhv4mn.11jx6aj1okcxpiN%cbarron3@ix.netcom.com>

rawhide <mark.rollins@yahoo.com> wrote:

I started working on a custom container class which would hold objects
which have iterators back to the container. I can't figure out how to
write it, not that its even possible. Here is uncompilable code which
illustrates the problem.

template <class T, class I>
class Item
{
      T object_;
      I iterator_;//this is the iterator back into the Item's container
};

template<class T>
class Container
{
      //impossible to compile yet illustrates my conundrum
      typedef Item<T, ContainerType::iterator> ItemType;
      typedef std::list<ItemType> ContainerType;

      ContainerType container_;
};

If possible, how can I get Item to know of its container's iterator
type?

    provide nested typedefs to provide nested types of the template
parameters like:

    template <class T,class I>
    Class Item
    {
    public:
         typedef T object_type;
         typedef I iterator_type;
     private:
         T object__;
         I iterator_;
         // ...
      public:
         // ...
         // get a copy of iterator_
         I get_iterator() const {return iterator_;}
    }

    template <class Data>
    void foo(Data &x)
    {
         typename Data::iterator_type it = x.get_iterator();
        // use it.
    if

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