Question

After reading this article: Using Interfaces in C++

I have decided to use the __interface keyword with a macro that will add virtual destructors as described in the above link.

I was happy that the __interface keyword will cause the compiler to enforce interface rules, but I was disappointed when I took it for a test drive… It turns out that the __interface keyword does not enforce the rule that a method in the interface should not contain a method body.

I can of course add a macro for function methods but I don’t want to do this. Does anyone have any other suggestions?

EDIT: portability is a none issue for me because i must compile on both windows and linux so i will use the __interface keyword when i’m on windows and not on linux , that will be in order to enforce the below rules , which can’t be enforced via abstract base class:

1. Can inherit from zero or more base interfaces.
2. Can only contain public, pure virtual methods.
3. Cannot contain data members; properties are allowed.
4. Cannot inherit from a base class.
5. Cannot contain constructors, destructors, or operators.
6. Cannot contain static methods.

besides the destructor issue which can be workaround one can see the advantage of using this keyword in windows env of course.

Answer 1

__interface is a microsoft specific extension. It’s not standard and not portable.

Also, C++ allows for pure virtual method to have function body.

class Base {
  virtual void foo () = 0;
};
void Base::foo ()
{ } // ok

It’s advisable to explicitly declare virtual destructor in the class body.