nested class in C++

Nested classes in C++ are essentially static nested class.
Non-static ones like in Java would be a bit harder to emulate in C++, because there is no compiler magic to automatically provide the context of the outer class. You would have to work around the issue by storing a reference to the outer class in the inner class, initialising it in the constructor of the inner class, and accessing members of the outer class explicitly via the reference.
```
#include<iostream>
using namespace std;

class A {
public:
    class B {
    private:
      int num;
    public:
      void getdata(int n) { num = n; }
      void putdata() { cout<<"The number is "<<num<<endl; }
   };
   
   void f() {
        B obj;
        obj.getdata(9);
        obj.putdata();
    }
};

int main() {
    A a;
    a.f();
   
    A::B b;
    b.getdata(9);
    b.putdata();
    return 0;
}
```
Output:
```
The number is 9
The number is 9
```
Home