Solved

interacting with elements of a templated container

Posted on 2006-11-08
4
210 Views
Last Modified: 2010-04-02
Hi,

I made a templated container class for testing out templates. It is a simple doubly linked list. Previously I had specified the exact type the container used so there were class specific operations in there, one of which was dumping the contents of the container (just pseudo code):

    class CLinkedList {

         CSpecificClass *m_pLinkedList;

         void DumpToScreen()
         {
              while (m_pLinkedList) {
                   next->PrintContents();
              }
    };

Now CLinkedList uses templates for the data it stores and so what can I do for an operation to dump all the contents of the list since I don't know what the user is going to stick in there? I can't do anything really, can I? I'd have to do it externally now like:

     int main()
     {
          CLinkedList<CWhatever> list;
          list.AddNode(...);
          list.AddNode(...);
          list.AddNode(...);

          // Iterate through each element somehow out here since I know the type only outside, not internally:
          while (somehow iterate externally over the list's elements) {
              *it->Print();
          }
     }

I guess this is why stl implemented the iterators, I'd have to do the same thing?

Thanks
   
0
Comment
Question by:DJ_AM_Juicebox
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 86

Accepted Solution

by:
jkr earned 500 total points
ID: 17903843
Implementing iterators on your own might be some overkill for startng out, but you could do something like

    template<typename T>
    class CLinkedList {

        public:

        CLinkedList () { // default constructor

            m_pNodes = NULL;
            m_pCurrent = NULL;
        }

        CNode<T>* First() const { m_pCurrent = m_pNodes; return m_pCurrent;}
        CNode<T>* Next() const {

            if (!m_pCurrent) return NULL;

            m_pCurrent = m_pCurrent->m_pNext;

            return m_pCurrent;
        }

        private:
        CNode<T> *m_pNodes;
        CNode<T> *m_pCurrent;
    };

     int main()
     {
          CLinkedList<CWhatever> list;
          list.AddNode(...);
          list.AddNode(...);
          list.AddNode(...);

          // Iterate through each element somehow out here since I know the type only outside, not internally:
         CWhatever<CSomeType>* it = list.First();;
          while (it) {
              it->Print();

              it = list.Next();
          }
     }
0
 
LVL 86

Expert Comment

by:jkr
ID: 17903873
Ooops, remove the 'const' in the above, that should just be

        CNode<T>* First() { m_pCurrent = m_pNodes; return m_pCurrent;}
        CNode<T>* Next() {

            if (!m_pCurrent) return NULL;

            m_pCurrent = m_pCurrent->m_pNext;

            return m_pCurrent;
        }
0
 

Author Comment

by:DJ_AM_Juicebox
ID: 17903918
Yep that's perfect, thanks as always.
0
 
LVL 30

Expert Comment

by:Axter
ID: 17904234
Hi DJ_AM_Juicebox,
> I guess this is why stl implemented the iterators, I'd have to do the same thing?
>>I guess this is why stl implemented the iterators, I'd have to do the same thing?

Are you sure you need a link list.  Rarely is a link list the correct container type, and for most requirements, a std::vector type contianer is much more efficient and more appropriate.
Moreover, with a std::vector, you can use operator[] instead of iterators.

David Maisonave (Axter)
Cheers!
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Templates For Beginners Or How To Encourage The Compiler To Work For You Introduction This tutorial is targeted at the reader who is, perhaps, familiar with the basics of C++ but would prefer a little slower introduction to the more ad…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question