// — Compiled code snippet —

#include

class Actor
{
public:
virtual ~Actor() {}
};

class InteractiveActor
{
public:
virtual ~InteractiveActor() {}

// Calling private virtual function from non-virtual function
void Interact() { Interact_Implementation(); };

private:
// Here we declare private virtual function of the i-face
virtual void Interact_Implementation() = 0;
};

// InteractiveActor i-face powered actor
class InteractiveProp : public Actor, public InteractiveActor
{
private:
void Interact_Implementation() override { printf(“Wow!\n”); }
};

// Simple actor
class NotInteractiveProp : public Actor
{};

void Filter(Actor* ptr)
{
InteractiveActor* iptr = dynamic_cast(ptr);

if (iptr)
{
// We have successfully cast Actor-class-pointer-to-InteractiveProp-object to
// implementation of InteractiveActor i-face in InteractiveProp object
iptr->Interact();
}
else
{
// But in the case of Actor-class-pointer-to-NotInteractiveProp-object we have an iptr == nullptr
// because NotInteractiveProp does not implement InteractiveActor i-face
}
}

int main()
{
Actor* ptr1 = new InteractiveProp;
Actor* ptr2 = new NotInteractiveProp;

// This call prints ‘Wow!’
Filter(ptr1);

// But not this one
Filter(ptr2);
}