Here is a sample C++ question to find out the outcome.
#include <iostream>
#include <vector>
class A
{
public:
A(int n = 0) : m_n(n) { }
public:
virtual int f() const { return m_n; }
virtual ~A() { }
protected:
int m_n;
};
class B
: public A
{
public:
B(int n = 0) : A(n) { }
public:
virtual int f() const { return m_n + 1; }
};
int main()
{
const A a(1);
const B b(3);
const A *x[2] = { &a, &b };
typedef std::vector<A> V;
V y({ a, b });
V::const_iterator i = y.begin();
std::cout << x[0]->f() << x[1]->f()
<< i->f() << (i + 1)->f() << std::endl;
return 0;
}
The output I expected was "1 4 1 4" but the correct answer is "1 4 1 3".
From above,
x[0]->f()
i.e., x[0] is nothing but a pointer to an object of type A and calling f() returns 1.
x[1]->f()
i.e., x[1] is nothing but a pointer to an object of type A (base class pointer pointing to derived class object) and calls derived class f() that returns (3 + 1) = 4
I am not sure how this behaves when we add the objects a and b into a vector container and iterating them through const_iterator with inheritance
i->f()
I can understand this as i is just a pointer to the first element i.e., object a.
But what will happen here?
(i + 1)->f()
My understanding is that it points to the next element in the sequence i.e., object b and calling f() through derived class pointer should call its member function rather than base class one's?
