Finding the instance of an object when you know the key

[Patrice Nolin]

Hi,
 
I'm trying to do something but I'm wondering if my solution is the best.
 
We have some workflows where we receive the key of a object as a parameter
and we want to instantiate an object with that key.
 
Now, we will probably just define a method on each object that will search
and return the object found.
 
Is it the right approach ?
 
Is there a generic object or function that can be use for that ?
 
 
Thanks
 
Pat