Объявление объекта вложенного класса

template<class T> class A{
    //......
public:
    class B {
        int dd;
        int mm;
        int yy;
    public:
        B() { dd = 01; mm = 01; yy = 2000; };
        B(int d, int m, int y) { dd = d; mm = m; yy = y; };
    };
 
};

A::B

A<T>::B

A<A<T>::B>

A<int>::B obj;

typedef A<int>::B
        type;
    
A<type>::B obj;

A<A<T>::B>

A<A<int>::B>

#include <iostream>
 
using std::cout;
using std::endl;
 
class C {
 public:
  C() { cout << "Constructor of C called" << endl; }
 
  ~C() { cout << "Donstructor of C called" << endl; }
};
 
template <typename T>
class A {
 public:
  A() { cout << "Constructor of A called" << endl; }
  ~A() { cout << "Destructor of A called" << endl; }
 
  class B {
   public:
    B() { cout << "Constructor of A::B called" << endl; }
    ~B() { cout << "Destructor of A::B called" << endl; }
  };
};
 
void TestFreeC() {
  cout << "TestFreeC:" << endl;
  C free_c;
  cout << endl;
}
 
void TestFreeA() {
  cout << "TestFreeA:" << endl;
  A<C> free_a_for_free_c;
  cout << endl;
}
 
void TestNotFreeB() {
  cout << "TestNotFreeB:" << endl;
  A<C>::B not_free_b_of_free_a_for_free_c;
  cout << endl;
}
 
void TestFreeAForNotFreeB() {
  cout << "TestFreeAForNotFreeB:" << endl;
  A<A<C>::B> free_a_for_not_free_b_of_free_a_for_free_c;
  cout << endl;
}
 
void GoingCrazy() {
  cout << "They are coming!: " << endl;
  A<A<A<A<A<C>::B>::B>::B>::B> strange_thing;
  cout << endl;
}
 
int main() {
  TestFreeC();
  TestFreeA();
  TestNotFreeB();
  TestFreeAForNotFreeB();
  GoingCrazy();
}

A< A<int>::B > a;

template<class T> class A{
public:
class B{
};
};