Do I have to override functions in a base class?

Hello, everyone. I'm trying to get my head around overriding functions of a base class, in C++. In this code:

Code:

---

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

    virtual foo() {}
    virtual bar() = 0;
};

---

1. My understanding is that bar() must be overridden in any derived class that is instantiated. Correct?

2. Is it the case that any derived class may or may not implement its own constructor and/or destructor and/or foo(), and it's completely okay? In any combination?

Richard

1. Not "must" but "will". Unless you use the C++11 " = delete;" syntax in your derived class, a destructor is always generated.

2. In addition to what I said above, a constructor is also required. It doesn't have to be the same as the base class constructor, but without at least one you can't create the object.