How to ensure class template argument is derived from particular class Foo?

Question

Possible Duplicate:
C++ class template of specific baseclass

class Base
{
...
};

class Derived1 : public Base
{
...
};

class Derived2 : public Base
{
...
};

class Unrelated
{
...
};

I want to have a class template ClassTemplate that accepts as parameter only classes Derived1 and Derived2 but not Unrelated, so I can do:

ClassTemplate<Derived1> object1;

ClassTemplate<Derived2> object2;

but I shouldn't do:

ClassTemplate<Unrelated> object3;

Is it possible at all?

Answer 1

Use boost static assert in combination with type traits

Answer 2

Use boost::is_base_of from Boost.TypeTraits:

template<class T> class ClassTemplate {
    BOOST_STATIC_ASSERT((boost::is_base_of<Base, T>::value));
};