copy assignment operator of class

Question

#include <iostream>
using namespace std;

class ClassA
{
  const int a;
  int b, c;
      public:
    ClassA(int x, int y):a(10)
    {
       b = x;
       c = y;
    }
    ClassA():a(10)
    {
    }
    void print()
    {
    cout << a << endl;
    }
};

int main()
{
  ClassA objA(10, 20);
  ClassA objB;
  objB = objA;
  objB.print();
  return 0;
}

compiler doesn't create copy assignment operator in the following cases:

Class has a nonstatic data member of a const type or a reference type.
Class has a nonstatic data member of a type which has an inaccessible copy assignment operator.
Class is derived from a base class with an inaccessible copy assignment operator.

In the above cases i understood the case 1 with above example. but i am not getting case 2 and case 3 so please help me to understand with some example.

This is pretty much a duplicate of http://stackoverflow.com/questions/4338073/implementation-supplied-copy-constructor-and-assignment-operator (Look at aschepler's answer there for an example for case 3). — jogojapan, May 27 '13 at 07:31

score 1 · Answer 1 · answered May 27 '13 at 07:28

Case 2 would be something like this:

class non_assignable { 
   // note: private
   non_assignable &operator=(non_assignable const &source);
};

class whatever { 
    non_assignable n;
};

Case 3 would be something like:

 class whatever : public non_assignable {};

In either case, a copy assignment operator won't be automatically generated for whatever because it includes a non_assignable member/sub-object, which has an inaccessible (private) copy assignment operator.

copy assignment operator of class

1 Answers1