How to inherit protected static member in c++?

@sallie 

In C++, it is not possible to directly inherit a protected static member from a base class. Protected static members are considered class-level variables and are not inherited by derived classes.

However, you can indirectly access the protected static member in the derived class by defining a public or protected member function in the base class that returns the protected static member. Then, you can call this function from the derived class to access the protected static member.

Here's an example:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

class Base {
protected:
    static int protectedStaticMember;

public:
    static int getProtectedStaticMember() {
        return protectedStaticMember;
    }
};

int Base::protectedStaticMember = 10;

class Derived : public Base {
public:
    void printProtectedStaticMember() {
        int value = getProtectedStaticMember();
        std::cout << "Value of protected static member: " << value << std::endl;
    }
};

int main() {
    Derived derived;
    derived.printProtectedStaticMember(); // Output: Value of protected static member: 10

    return 0;
}

In this example, the base class Base defines a protected static member protectedStaticMember and a public static member function getProtectedStaticMember() that returns the value of protectedStaticMember. The derived class Derived then calls getProtectedStaticMember() to access the protected static member and print its value.

Note that while the derived class can access the protected static member through the public or protected member function, it does not actually inherit the protected static member itself.

@sallie 

Here is a code example illustrating how to inherit a static member in C++:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

#include <iostream>

class Base {
protected:
    static int protectedStaticMember;

public:
    Base() {
        // Initialize the protected static member in the base constructor
        protectedStaticMember = 100;
    }

    static int getProtectedStaticMember() {
        return protectedStaticMember;
    }
};

int Base::protectedStaticMember; // Define the static member

class Derived : public Base {
public:
    void printProtectedStaticMember() {
        int value = getProtectedStaticMember();
        std::cout << "Value of inherited protected static member: " << value << std::endl;
    }
};

int main() {
    Derived derived;
    derived.printProtectedStaticMember(); // Output: Value of inherited protected static member: 100

    return 0;
}

In this example, the Base class has a protected static member protectedStaticMember and a public static member function getProtectedStaticMember() to return its value. The Derived class inherits from Base and can access and use the protected static member through the inherited member function getProtectedStaticMember().

When you create an instance of Derived and call printProtectedStaticMember(), it will print the value of the inherited protected static member.

Remember that static members are associated with the class itself and not with instances of the class. In this example, the static member is initialized in the base class constructor, but it remains the same for all instances of both the Base and Derived classes.