如何在声明之外定义一个专用于无参数的可变参数模板类的C ++方法？

Question

I have a variadic templated class that I want to specialize to take no parameters and then I want to define methods outside the class declaration.

But the following gives

error: template-id ‘foobar<>’ for ‘foobar<>::foobar()’ does not 
match any template declaration

What am I doing wrong?

template <typename ...> class foobar;

template <>
class foobar <> 
{
    foobar();
};

//does not work!?
template <>
foobar<>::foobar() {};

Answer 1

The constructor isn't a template, since it's a non-template member of a full specialisation, so it doesn't need template in its declaration:

// does work
foobar<>::foobar() {}