inheritance.cpp

#include <iostream>

class BaseClass {
public:
    void say_hello() { 
        std::cout << "Hello";
    }
protected:
    void say_world() {
        std::cout << "world!";
    }
};

class PublicInheritance : public BaseClass {
};

class ProtectedInheritance : protected BaseClass {
};

class PrivateInheritance : private BaseClass {
public:
    void say_hello_world() {
        say_hello();
        say_world();
    }
};

class TestProtectedClass : public ProtectedInheritance {
public:
    void say_hello_world() {
        say_hello();
        say_world();
    }
};

class TestPrivateClass : public PrivateInheritance {
public:
    void say_hello_sam() {
        // This will not be OK as also protected functions and members
        // will become private due to private inheritance
        // say_hello();
    }
};

int main()
{
    PublicInheritance pub;
    pub.say_hello(); // OK
    
    ProtectedInheritance prot;
    // This will not be OK as say_hello will become protected function
    // because of protected inheritance being used.
    // error: 'void BaseClass::say_hello()' is inaccessible within this context
    // prot.say_hello(); 
    
    PrivateInheritance priv;
    // This will not be OK as say_hello will become private function
    // because of private inheritance being used.
    // error: 'void BaseClass::say_hello()' is inaccessible within this context
    // priv.say_hello();
    
    // This will be OK as the say_hello is private function due to 
    // private inheritance so inheriting class can access it
    priv.say_hello_world();
    
    TestProtectedClass clazz;
    // This will be OK as the say_hello is protected function due to 
    // protected inheritance so inheriting class can access it
    clazz.say_hello_world();
}