inner_template_inheritance.cpp

// Example program
#include <iostream>
#include <string>

using namespace std;

template<typename T>
class A
{
public:
    template<typename U>
    class B;    
    
    /*
    class D : public B<int>
    {
    public:
        void method2() {
            cout << "Method 2" << endl;
            this->method1();
        }
    };
    */
    
    class D;
};

template<typename T>
template<typename U>
class A<T>::B 
{
public:
    void method1() {
        T x;
        cout << "Method 1: " << x << endl;
    }
};

template<typename T>
class A<T>::D : public A<T>::B<int>
{
public:
    void method2() {
        cout << "Method 2" << endl;
        this->method1();
    }
};

int main()
{
  A<int>::D b;
  b.method2();
}