[Rails-devel] Undo / Redo design

[brett l. <wak...@gm...>]

I've been thinking about how to approach implementing Undo/Redo.

It seems to me that there are two basic strategies that we can attempt.

In each of them, we need to create a stack to store actions. Then, we
can place the stack in front of or after the code to execute the
action.

The basic flow would look something like this:

Stack before Action (Stack as EventHandler):
1. Stack object receives call from UI to take an action.
2. Stack stores action taken
3. Stack object calls model object to resolve action.

Stack after Action (Stack as a Listener):
1. Model code receives call to act.
2. Model resolves action
3. Model notifies Stack object of action just taken.


I haven't really done much of an analysis of which approach would be
more work or have additional implications.  There also could be other
approaches I haven't thought of, as well.

What are your thoughts on this?  Is there a solution with an obvious advantage?


----Brett.