How to call base class's function that is not defined in derived class? [duplicate]

Question

I always thought public methods of base class do get inherited by the derived class, even thought the derived class did not had definition of that particular method. For example

#include <iostream>

using namespace std;


    class A {
    public:
        int f() { cout << 3; return 0;}
        int f(int x) {cout << x; return 0;}
    }; 

    class B: public A {
    public:
        int f() {std::cout << 5; return 0;}

    };


    int main(){
       B ob;
       ob.f(7); 

       return 0;
    }

I was expecting the result to be : 7 , but I get compilation error saying

" error: too many arguments to function call, expected 0, have 1; did you mean 'A::f'?"

I know what the error is trying to say but I am little confused that the fuction from the Base class is not called.

overloading a function in derived class hides all base class versions — Gaurav Sehgal
– Gaurav Sehgal, Commented Jun 14, 2016 at 4:57
I found a link from stackoverflow - stackoverflow.com/questions/411103/… which explains the question lucidly. — pokche
– pokche, Commented Jun 14, 2016 at 5:01

Gaurav Sehgal · Accepted Answer · 2016-06-14 05:01:20Z

7

Overloading a method in a derived class hides all base class versions.Even if the signature is different.If a method with the same name as in base class, exists in derived class then you won't be able to directly call base class versions.

You can do

  ob.A::f(7);

answered Jun 14, 2016 at 5:01

Gaurav Sehgal

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Comments

R Sahu · Accepted Answer · 2016-06-14 05:09:56Z

2

With your posted code, B::f shadows all versions of A::f. You can call A::f(int) from an object of type B by using couple of methods.

Use A::f explicitly.
```
B ob;
ob.A::f(7); 
```

Bring all versions of A::f into the scope of B.

class B: public A {
   public:
      using A::f;
      int f() {std::cout << 5; return 0;}

};

Now you can use:

B ob;
ob.f(7);

answered Jun 14, 2016 at 5:09

R Sahu

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2 Comments

asad_hussain Over a year ago

@ R Sahu ,but the above case works in Java.

R Sahu Over a year ago

@a874, I am not familiar with Java. I can't comment on that. However, that has nothing to do with whether it works in C++.

Sumeet · Accepted Answer · 2016-06-14 05:13:57Z

2

You can use another way:

class B: public A {
    public:
        using A::f;
        int f() {std::cout << 5; return 0;}

    };

answered Jun 14, 2016 at 5:13

Sumeet

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