I realy don't understand why it works, but below code shows an example of calling private method from the world without any friend classes:
class A
{
public:
virtual void someMethod(){
std::cout << "A::someMethod";
}
};
class B : public A
{
private:
virtual void someMethod(){
std::cout << "B::someMethod";
}
};
int main(){
A* a = new B;
a->someMethod();
}
outputs:
B::someMethod
Doesn't it violates encapsulation rules in C++? For me this is insane. The inheritance is public, but the access modifier in derived class is changed to private, thus the someMethod()
in class B is private. So in fact, doing a->someMethod()
, we are directly calling a private method from the world.
Consider the following code, a modification of the code in the original question:
class A
{
public:
virtual void X(){
std::cout << "A::someMethod";
}
};
class B : public A
{
private:
virtual void Y(){
std::cout << "B::someMethod";
}
};
int main(){
A* a = new B;
a->X();
}
It's easy to understand that it's legit to call X(). B inherits it from A as a public member. Theoretically if X() would call Y() this would be legit as well of course, although this is not possible because X() is declared in A which doesn't know Y(). But actually this is the case if X = Y, i.e. if both methods have the same name.
You may think of it as "B inherits a public method from A, that calls a private method (of B) with the same name".