How can i call the base class show() withe the help of virtual function?

Question

1.00/5 (1 vote)

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C++

#include <iostream.h>
#include <conio.h>

class A
{
      public:
             void show()
             {
                  cout<<"Class A's show()";
             }
};

class B : public A
{
      public:
             void show()
             {
                  cout<<"Class B's show()";
             }
};

int main()
{
    B o;
    o.show();
    getch();
    return 0;
}

Posted 3-Aug-11 0:29am

Ashutosh_g

Updated 3-Aug-11 0:49am

CPallini

v3

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CPallini · Answer 1 · 2011-08-03T00:47:00

Solution 1

Virtual functions won't help you on that (unless you call the base class method in the derived class one).
However, since B is A you may do:

C++

int main()
{
  B b;
  b.A::show();
}

Posted 3-Aug-11 0:47am

CPallini

Updated 3-Aug-11 0:48am

v2

Comments

Sergey Alexandrovich Kryukov 3-Aug-11 18:43pm

Correct, my 5. I added just my two cents to it, please see.
--SA

వేంకటనారాయణ(venkatmakam) · Answer 2 · 2011-08-03T01:02:00

Solution 2

Adding to Cpallini solution,

you can do like this,

C#

class B : public A
{
      public:
             void show()
             {
                  cout<<"Class B's show()";
                  A::show();   //call base class show().
             }
};

Posted 3-Aug-11 1:02am

వేంకటనారాయణ(venkatmakam)

Comments

Sergey Alexandrovich Kryukov 3-Aug-11 18:42pm

Correct, a 5. I added just my two cents to it, please see.
--SA

Sergey Alexandrovich Kryukov · Answer 3 · 2011-08-03T12:42:00

Solution 3

Just a note: you did not override show in derived class as both functions are not virtual, you have simply hidden the function of the base class; so the resolution shown by CPallini and venkatmakam is needed. Using virtual function means that the overridden version replaces the function entry in the vtable of derived class. I'm afraid to say: if you don't understand it, you have no idea of OOP — just yet. You really need to learn it.

—SA

Posted 3-Aug-11 12:42pm

Sergey Alexandrovich Kryukov

Comments

CPallini 4-Aug-11 10:28am

My 5.
You know, my resolution (or venkatmakam's) is needed even if he/she overrides show.

Sergey Alexandrovich Kryukov 4-Aug-11 15:36pm

Thank you. I agree: you resolve inherited hidden function or inherited implementation of a virtual function in the same way, even though its run-time dispatching is quite different. Good point.
--SA