Operator == with double dispatch in C ++

Question

How to implement

operator==(const Base& base)

to compare subclasses of st, calls will be correctly sent when called

Base* base1 = new Derived1();
Base* base2 = new Derived2();
base1->operator==(*base2)?

Answer 1

• Execute the == operator as a function of free standing.
• Ask him to call a virtual method for one of the arguments (for example, IsEqual ())

It brings you to what you have.

Derived1::IsEqual(const Base& base)

Called. From here you have several options

• Use RTTI for dynamic_cast <> base to Derived1

• If the number of derivatives is small and of course you can implement

  virtual bool Base::IsEqualToDerived(const Derived1& d) {return false};
  virtual bool Base::IsEqualToDerived(const Derived2& d) {return false};
  

like virtual methods. In Derived1, you override and compare for real.

Answer 2

++ , ==. , , , , dynamic_cast