Thread: class schema implementation doubt

  1. #1
    Registered User
    Join Date
    Jun 2008

    class schema implementation doubt

    Hi ,

    This is the scenario of the problem I am trying to solve ..

    A class 'A' has an object of class 'B'

    From the object of class B , I need to tell the object of class A, to execute a particular function.

    Could you help me with the schema?

    I get compiler errors, when I try to implement this.

    I have uploaded the the schema I tried..


  2. #2
    The larch
    Join Date
    May 2006
    If A contains an instance of B, it must know all about B. Therefore B must come first (or included from a header).

    B however doesn't contain an instance of A (it couldn't). Instead it just has to know that a class by the name A exists, so it can declare pointers to it. For that forward declarations are used.

    All in all the layout would be:
    //forward declaration of A
    class A;
    //declaration of B
    class B
    //declaration of A
    class A
        //we know all about B:
        B b;
    //now we also know all about A and can implement the function in B
    //that needs to know about A's member functions
    void B::set_pointer(A* a) {...}
    Other notes:
    main() should have an explicit return type (C++ does not accept defaulting return types).

    A little indentation wouldn't hurt.

    A a= A();
    This, of course, is the same as
    A a;
    except potentially calling one constructor and one destructor less.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

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