Need to be enlightened on Parent, Child object assignments

Question

Hi!
I am too boggled with parent class, child class objects assignments. For example say I have something like this:
class parent{
   int a;
    void doStuff(){...}
class child extends parent{
int b;  
void doOtherStuff(){...}
}Ok. Now. if have have something like this:
parent p;
child c;Then which one of the below is legal and why and why not?
1.) c = p;
2.) p = c;
I think p = c is legal. If so, can I do p.a =12; p.b=15;
Why and why not?
Please be my lifesaver.
Thank You for reading!

Answer 1

parent p;
child c;
If these are defined as global variables then both p and c will be null, meaning they refer nothing. Since a child inherits properties of the parent you can hold a child object using a parent reference
so this is legal
p = c;
(Note: you need to understand the concept of a reference and object well. Here p and c are both references not objects).
When you hold a child object using a parent's reference only parent's properties are visible. If you want to see the child's properties then you need to cast that reference to a child reference. So you can't say p.b=12.
Hope you got what you want