Making a class abstract without any pure virtual methods

Question

I take a class where we watch mouse activities.

However, I do want to make it plain that the user must inherit it; I do not want to make them implement any particular one.

Exists a method to accomplish this?

Thanks

Answer 1

A pure virtual destructor can be declared, but it must have a definition. 

Although the class will be abstract by default, any derived classes won't be.

struct Abstract
{
     virtual ~Abstract() = 0;
};

Abstract::~Abstract() {}

struct Valid: public Abstract
{
        // Notice you don't need to actually overide the base
        // classes pure virtual method as it has a default
};


int main()
{
    // Abstract        a;  // This line fails to compile as Abstract is abstract
    Valid           v;  // This compiles fine.
}