Question

I have a weird issue using polymorphism.
I have a base class that implements a static method. This method must be static for various reasons. The base class also has a pure virtual method run() that gets implemented by all the extended classes. I need to be able to call run() from the static class.

The problem, of course, is that the static class doesn’t have a this pointer. This method can be passed in a void * parameter. I have been trying to come up with a clever way to pass the run method into it, but nothing has worked so far. have also tried passing this into it. The problem with this is that I would then have to instantiate it, which requires knowledge of the extended class. This defeats the whole purpose of the polymorphism.

Any ideas on how to go about this?

Answer 1

Don’t pass it as a void* pointer, pass it as a pointer (or reference) to the base class:

class BaseClass
{
public:
  static void something(BaseClass* self) { self->foo(); }
  virtual void foo() = 0;  
};