Modifying has_many list without saving

I have a multi-page form which creates/edits an event (model held in
session) and it's invites. When the event is edited I want the user
to be able to modify the invites without saving. For example:

   invite = Invite.new "test@test.com
   event.invites << invite

Right now this automatically adds that invite to the database. How
can I keep it from doing this until I call "event.save"? I was
thinking about doing a clever validation hook, until I considered
deleting invites:

   event.invites.delete(invite)

That will delete from the database before calling "event.save()",
which means the user cannot cancel this action by canceling the flow.
Currently I'm saving the event object in the session.

The user should be able to modify the invitations list all they want
without it being final until they finish the flow.

Any ideas?

So far the only thing I can think of is either keeping the invite
associations separate and baking them into the event at the end or
creating a new event "clone" at the beginging and merge at the end.
Neither of these seem like a graceful solution.

Thanks,
Jeremy

I don't know for sure if its changed in 2.x
However, in 1.1.6 I believe that if you do it the other way around such
as

=============================
invite.event = event

it won't save automatically.

You're right, this way it wont save the invite, however, it also wont
update the event invite list either. (i.e. "event.invites")

This is for a 3 page flow where invite management is on the first
page. The user should be able to modify the invite list and if they
cancel out of the flow (or close their browser), it should not update
the database. This is why I don't want anything to save anything
until the last page of the flow.

It would be really helpful if the event invite list were to update
(without saving) as the user make changes. This way I can show the
current list as they tweak it.

Thanks for the suggestions

- Jeremy

Semantic argument:

ROA States: HTTP is stateless, so too should your application be.

Laymen explanation: Don't use the session lest you have to.

Helpful alternative: Store the state of the resource (not the same as
application state).
Allow the save.
Include a created_at field.
If invitation is not sent within X days destroy the invitation.

Ever Helpful Alternative( not advised but what the hell ):
Store the invitations in a separate array (not through the association
and associate them on completion of the form

This works when the user creates the event, but what about when they
try to modify it. If the event is saved every step of the flow, the
user wont be able to cancel out of it. Generally users expect
everything in a flow to be temporary until they click "Finish" on the
last page.

I hate storing the event in session, but don't know of a better way to
support a multi-page flow in both create and edit modes.

Thanks