如何访问嵌套的 class 的私有成员？

Question

A.hpp

class A
{
  public:
  class B
  {
    int x;
  public:
    B(int f);
  };
  void alpha(B *random);
};

A.cpp

void A::alpha(A::B *random)
{  
  // access x here, how to do it?
}

The private variable is getting set at some place and I want to access that value in this alpha function. How can I access x inside alpha() ?

EDIT: 2nd Question: A.hpp

class A
{
  public:
  class B
  {
    int x;
  public:
    B(int f);
  };
  virtual void alpha(B *random) = 0;
};

C.hpp

class C : public A
{
  public:
  virtual void alpha(B *random);
};

C.cpp

void C::alpha(A:B *random)
{  
  // access x here, how to do it? 
}

Answer 1

You can make class A a "friend" of class B which allows A to access private members of B

combining your files for ease of compilation:

class A
{
  public:
  class B
  {
    friend class A;  // *** HERE ***
    int x;
  public:
    B(int f);
  };
  void alpha(B *random);
};



void A::alpha(B *random)
{
    int x = random->x;
}

int main() {}

Answer 2

A class can access another class's private members if it's a friend of that other class, like in this example:

class A {
 public:
  class B {
    friend class A;
    int x;

   public:
    B(int f);
  };
  void alpha(B *random) { random->x = 10; }
};