Template inheritance with specialization example

gistfile1.txt

#include <iostream>
#include <vector>

template <typename T>
struct Foo {
    T t;
};

template <typename T>
class Base {
public:
    typedef Foo<T> Bar;
    typedef std::vector< Foo<T> > BarVec;
    virtual BarVec BazVec() = 0;
    virtual Bar Baz() = 0;
};

template <typename T>
class Derived : public Base<T> {
public:
    typedef typename Base<T>::Bar Bar;
    typedef typename Base<T>::BarVec BarVec;
    //virtual typename Base<T>::Bar Baz();
    virtual BarVec BazVec();
    virtual Bar Baz();
};

template <>
typename Derived<int>::BarVec Derived<int>::BazVec() {
    Derived<int>::BarVec bvec;
    Derived<int>::Bar bar;
    bar.t = 4;
    bvec.push_back(bar);
    bvec.push_back(bar);
    return bvec;
}

template <>
typename Derived<std::string>::BarVec Derived<std::string>::BazVec() {
    Derived<std::string>::BarVec bvec;
    Derived<std::string>::Bar bar;
    bar.t = "abc";
    bvec.push_back(bar);
    bvec.push_back(bar);
    return bvec;
}


template <typename T>
typename Derived<T>::Bar Derived<T>::Baz() {
    return BazVec()[0];
}

/*template <typename T>
typename Derived<T>::Bar Derived<T>::Baz() {
    return Base<T>::Bar;
}

template <>
typename Derived<int>::Bar Derived<int>::Baz() {
    Derived<int>::Bar r;
    r.t = 3;
    return r;
}*/

int main(){
    {Derived<int> d;
    //Foo<int> gg = d.Baz();
    Foo<int> gg = d.Baz();
    std::cout << gg.t << std::endl;}

    {
    Derived<std::string> d;
    //Foo<int> gg = d.Baz();
    Foo<std::string> gg = d.Baz();
    std::cout << gg.t << std::endl;
    }
    return 0;
}