RC is part of your Handler, your model wouldn't know anything about it
and shouldn't. Your model knows about the values that are sent into
it. Once they are sent in, they are part of the Arguments collection.
Abstracting away from the particulars of the populateModel and
populateBean methods, think of it this way.
Lets say your User bean takes 3 pieces of info, a first name, a last
name and an email address and you have an init function that invokes
your setters. All three of the following ways to create the User bean
would be equally valid:
Your User object doesn't care where the data is coming from. It just
gets a value for a first_name and does, internally,
instance.variables.first_name = arguments.first_name
Everything it sees comes in via the arguments scope. How you pass data
into object is your choice.
The populateModel and populateBean methods are convenience methods
that scan the request collection, which is itself a convenience
structure combining the url and form scopes, and uses the values to
send in matching arguments to your object, thus populating the
arguments structure of your object.
In a nutshell, your object should never know about the request
collection. All it knows about is the arguments scope. Hope that
helps. If you need further clarification, holler.