Object from database record

I have a problem with creating objects from database records.
In the model Room I have declared instance variable (at the beginning
of a class)

@exits = {:south=>nil, :north=>nil}

The database has been already populated with rooms.

Now, if somewhere in a program i use Room.find(1), I get the object
room, however it doesn't see the @exists hash. How can I make it see
it?
I'm totally new to RoR and this being probably straightforward problem
just drives me maaad. Help please.

I think not... Basically I want to have an instance variable, that is
not related to any column from the database mapped to the object. And
I want to be able to see that instance variable when creating the
object through ModelName.find(id).