C++ Tutorial/Class/private inheritance

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Granting Access: Inherit base as private

#include <iostream>
using namespace std;
   
class base {
  int i; // private to base
public:
  int j, k;
  void seti(int x) { i = x; }
  int geti() { return i; }
};
   
// Inherit base as private.
class derived: private base {
public:
  base::j; // make j public again - but not k
  base::seti; // make seti() public
  base::geti; // make geti() public
   
  int a; // public
};
   
int main()
{
  derived ob;
   
  ob.j = 20; // legal because j is made public in derived
   
  ob.a = 40; // legal because a is public in derived
  ob.seti(10);
   
  cout << ob.geti() << " " << ob.j << " " << ob.a;
   
  return 0;
}

how to use an access declaration

#include <iostream>   
     using namespace std;
  class B_class {   
  public:   
    int i, j;   
  };   
       
  class D_class : private B_class {   
  public:   
    // access declaration   
    B_class::i;  // i from B_class is now public again   
       
    int k;   
  } ;   
       
  main(void)   
  {   
    D_class d;   
       
    d.i = 10;  // legal because i is made public in D_class   
    d.k = 20;   
       
    cout << d.i * d.k;   
       
    return 0;   
  }

Inherit base as private

#include <iostream>
using namespace std;
class base {
private:
  int i;
public:
  int j, k;
  void seti(int x) { i = x; }
  int geti() { return i; }
};
class derived: private base {
public:
  base::j;
  base::seti;
  base::geti;
  int a;
};
int main()
{
  derived ob;
  ob.j = 20; // legal because j is made public in derived
//ob.k = 30; // illegal because k is private in derived
  ob.a = 40; // legal because a is public in derived
  ob.seti(10);
  cout << ob.geti() << " " << ob.j << " " << ob.a;
  return 0;
}
10 20 40"
Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/Class/private_inheritance&oldid=2325»