C++ Abstract class can't have a method with a parameter of that class

Question

I created this .h file

#pragma once

namespace Core
{
    class IComparableObject
    {
    public:
            virtual int CompareTo(IComparableObject obj)=0;
          


        

Answer 1

From C++03, §10.4 3:

An abstract class shall not be used as a parameter type, as a function return type, or as the type of an explicit conversion. Pointers and references to an abstract class can be declared.

Passing obj as a const reference is allowed.