I was thinking about creating copy constructor for `A` class but I'm not sure which approach to take

Question

I was thinking about creating copy constructor for A class but I'm not sure which approach to take.

class A {
  private:    
    int a;
    int b;

  public:     
    A() { a = 0; b = 0; }
    int gA() { return a; }
    int gB() { return b; }

};                  

class B {
  private:
    int *x;
    int *y;
  public:     
    B() { x = 0 y = 0; }
    int* X() { return x; }
    int* Y() { return y; }
};

Answer 1

Your code has two problems:

1. There is no way of creating an Alpha object or a Beta object that is not all zero, so Alpha a1 = aBetaObject; cannot do anything useful.

2. The get methods are not const , so they can't be used in const contexts. You should ensure const correctness by marking the get methods as const .

You need to fix these two problems first.

Then, to support Alpha a1 = aBetaObject; and a2 = aBetaObject; , you need to provide a constructor to allow Alpha to be initialized with Beta .

Alpha(const Beta& beta)
    :a{*beta.getX()}, b{*beta.getY()}
{
}

Note that this is undefined behavior when beta.x or beta.y is a null pointer. You can make a check:

Alpha(const Beta& beta)
{
    if (beta.getX() && beta.getY()) {
        a = *beta.getX();
        b = *beta.getY();
    } else {
        throw std::invalid_argument{"blah blah blah"};
    }
}

Or you can make sure that beta.x and beta.y are never null, which doesn't seem to be the case here.