Calling a base class method in a template virtual class hierarchy

Question

Let\'s say I have the following class hierarchy:

template< class T >
class TestBase {

public:

    virtual T const & do_foo() = 0;

};

template&l         


        

Answer 1

It will not win any awards for it's beauty, but this piece of code works as expected, without the compiler complaining.

virtual int do_bar() {
    return ((TestBase<T> *) this)->do_foo() + 1;
}

Answer 2

Non-dependent names (that is, names which do not depend on template arguments), are looked up when parsing the template, not when instantiating it. You need to make do_foo a dependent name. There are basically two ways to achieve this:

virtual int do_bar() {
    return this->do_foo() + 1;
}

or

template< class T >
class TestDerived : public virtual TestBase< T > {

public:
    using TestBase<T>::do_foo;

    virtual int do_bar() {
        return do_foo() + 1;
    }

};