Re: Enable Polymorphism on Run()

Victor Bazarov <>
Thu, 30 Apr 2009 16:48:26 -0400
Immortal Nephi wrote:

     I am trying to enable polymorphism. I created three derived classes
as B1, B2, and B3. class B1, B2, and B3 are derived from class A.
Only one virtual function Run() is invoked to select class B1, B2, or
B3 from class A.
    I do not want to reassign reference of class B1, B2, and B3 to class
A pointer inside main() body. They can be done inside Run() body.
When you compile and run my source code, Run() is always invoked to
class B1 each time.
    Please assist me to make the correction. Thanks for your advice.

#include <iostream>

class A

    A() : regA(0), regX(0), regY(0)
        cout << "A()\n";

        cout << "~A()\n";

    void virtual Run(A* pa, A& ra)

If you are going to assign to 'pa' and hope to keep the change outside
of this function, 'pa' cannot be passed by value, otherwise the new
value (after assignment) only exists inside 'Run' function and the
caller does not know about it. Try printing the value of 'pa' in 'main'
right after each call to 'Run'...

        cout << "A::Run()\n";

    int regA;
    int regX;
    int regY;

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