Thread: Access via iterator to pointer container

  1. #1
    Registered User
    Join Date
    Jul 2009

    Access via iterator to pointer container

    I am a c++ newbie and I am trying something very similar. Here's my code -

    class A
      Pointer * p;
      double d;
    class B:public A
    int main()
     for (list<B *>::const_iterator it = listeB_.begin(); it!=listeB_.end(); it++)
                    cout << (it->p)->getNumero() << endl; 
    The error is 'request for member 'p' in ...., which is of non-class type ....

    Basically, I need to print the value for p. Where am I going wrong?

    Thanks for your help in advance.


  2. #2
    and the Hat of Guessing tabstop's Avatar
    Join Date
    Nov 2007
    it is a iterator over a list<B *>, therefore if you dereference it (which you do with the -> notation), you get a ... B*, and not a B. Therefore the left hand side is not a class, and therefore any attempt to access a member will fail miserably. You will need to take it, dereference it once to get a B*, and then again to get a B; so something like (*it)-> ....

  3. #3
    Cat without Hat CornedBee's Avatar
    Join Date
    Apr 2003
    Your current problem doesn't actually have anything to do with the other thread, so I split this off. But even if it did have something to do, you should create a new thread and link the old one instead of taking over.

    Your first problem is that you have an iterator over a container holding pointers. Let's keep in mind that a->b is supposed to be semantically equivalent to (*a).b
    What is the type of (*it) in your example? Because the container is of B*, the type of (*it) is also B*, on which you can't use the dot operator. To access the members of B, you need to do (*it)->member.

    But that doesn't resolve your other problem. You're outside B. You have no access rights to B's non-public members, no matter where they come from. If you need that access, you have a design problem, and we'll need more information to help you with that.
    All the buzzt!

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