CODEWITHSUNDEEP
c++inheritance
MAR
MAR

Reputation: 103

Prevent Child class from accessing protected member variable of "Grandparent" class

I have a base class called "Grandparent" with a special protected member variable like:

class Grandparent
{
protected:
   MyClass m_obj;
}

I have a class "Parent" that derives from this and monitors access to the m_obj member variable with special getters and setters:

class Parent : Grandparent
{
protected:
   void setObj(val) { m_obj = val; }
   MyClass getObj { return val; }
}

Finally, I have a class "Child" that inherits from Parent and uses those setObj and getObj methods in Parent:

class Child : Parent
{
  //some other methods that call getObj and setObj
}

My issue is, I want to force the Child class to use the getters and setters in the Parent class, rather than being able to access the m_obj variable in the Grandparent class directly. I do not have privileges to edit the Grandparent class, only the Parent and Child classes. How do I do this?

Upvotes: 0

Views: 502

Answers (2)

MAR
MAR

Reputation: 103

MatG's comment about searching "c++ inheritance change member access specifier" answered by question. I didn't realize you could change the access modifier of a parent class member in a derived class.

class Parent : Grandparent
{
protected:
   void setObj(val) { m_obj = val; }
   MyClass getObj { return val; }
private:
   using Grandparent::m_obj;
}

Upvotes: 4

Zoso
Zoso

Reputation: 3465

How about changing the current Parent is-a Grandparent relationship to Parent has-a Grandparent one? You would have the options of Composition or Private Inheritance to choose from but given that you're having an inheritance between Parent and Grandparent currently and that m_obj is a protected member of Grandparent, I'd gather it would be more convenient to just switch to Private Inheritance since you'd still have access to all the public/protected functions/data of the Grandparent class as it is. Now with this change, since m_obj would become a private member of Parent, Child wouldn't have access to it, and using setters/getters would be the only option for the Child to use.

Upvotes: 0

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