C++ Pointers and Incomplete Types

Learned some new things about C++ and pointers today. Namely that you can declare a pointer member variable of the class A in class A. Pretty neat. Take for example the following simple illustration.

#include <iostream>
class A {
    public:
        void setMember(A& m) { this->member = &m; }
        A* member;
        int x;
};

int main(int argc, char** argv) {
    A a,b;
    a.x = 2;
    b.x = 3;
    a.setMember(b);
    b.setMember(a);

    std::cout << "a.member->x = " << a.member->x << "n";
    std::cout << "b.member->x = " << b.member->x << "n";
}

It's output is as follows:

a.member->x = '3'
b.member->x = '2'

So instead of doing this same thing in other more complicated ways we can do it in one class with simple pointers. Also note that we don't need to destruct the member variable since it will be destructed automagically. I find this technique useful in cases where it makes sense for classes to be linked together. In my case the different layers of a neural network.

Benjamin Snider