How come this works??

Unity Engine
1

class Base {}

class Item : Base {
public int myvariable;
}

some class {
list mylist;
mylist.Add(Item item1);
mylist.Add(Item item2);
item1.myvariable = some value; //doesnt work because list is of base type
((Item)mylist[1]).myvariable = some value; //this works when i cast but the list is of base type
}

Although both items were of Item type, why do i need casting to make it work?
How come they were added to the list in the first place anyways?

This thing works and ive no problem, but i need to know why it works.

EDIT: Although this works, ScriptableObject doesnt serialize myvariable.
But XML serializes it.

2

Because you store Base objects in your list and if you access them through the list, it basically returns the Base object (which doesn’t have a variable called “myvariable”). Casting it from the Base object to the Item object gives you access to the variable. But pay attention though: If you store a object that is derived from Base but not Item (ie. class FooClass : Base), the cast will throw a type exception (since the derived class is not convertible to Item).

3

I see, but isnt this up casting now? I thought it was not possible.

Anyhow, thanks for clarification.

4

Technically it’s not upcasting because the item is of type Item. If the item was of type Base explicitly then a cast to Item would fail.