CODEWITHSUNDEEP
c++visual-studiovisual-c++inheritanceprivate
Pranit Kothari
Pranit Kothari

Reputation: 9841

How private inheritance allowed me to create object?

I have simple code, which I assume to be failed.

I have privately inherit Shield from Sealer, and even Shield is not it's friend, still I am able to create object of Shield. 

class Sealer
{
public:

    Sealer()
    {
        cout<<"base constructor;"<<endl;
    }

};

class Shield : private Sealer
{
public:

    void p()
    {
        cout<<"P gets called;"<<endl;
    }
};

int main()                          
{
    Shield d;  //success here
    d.p(); // here too
    return 0;
}

How it is possible? Base class constructor should not be accessible. Isn't it?

I am using Visual Studio 2012.

Upvotes: 0

Views: 122

Answers (3)

R Sahu
R Sahu

Reputation: 206567

When you use private inheritance, you cannot access the base class functionality through the derived class. You cannot create a base class pointer or a reference from the derived class.

class Sealer
{
   public:

      Sealer() {}
      void p()
      {
         cout<<"P gets called;"<<endl;
      }

};

class Shield : private Sealer
{
};

int main()                          
{
    Shield d;
    d.p();         // Not allowed.
    Sealer& p = d; // Not allowed.
    return 0;
}

Upvotes: 0

Matthew Read
Matthew Read

Reputation: 1861

class Shield : private Sealer means that everything in Sealer is kept private within Shield; it cannot be seen outside Shield or in classes derived from it.

It does not magically go back and make Sealer's constructor private so that Shield cannot access it. What would be the point of private inheritance if the child class could not access anything from the base class? It would do exactly nothing.

Upvotes: 1

Jean-Baptiste Yun&#232;s
Jean-Baptiste Yun&#232;s

Reputation: 36391

This does not means that Sealer is private relative to Shield (Sealer member access from Shield is controlled via access category declaration), it simply means that the inheritance is private, means that this is not externally observable (you can manipulate Shield as you like but not has Shield instance).

Upvotes: 0

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