Rails 3 - Process text input to create multiple models

In the app I'm working on, Courses have many Problems, which in turn have many Steps. Right now there is a form for adding Problems to Courses (and then Steps can be added to those problems). What we want is to have a form that just has a field for LaTeX input, and then process the TeX to create multiple problems with their steps.

At the moment, we're doing this all in the Problems controller. We have two methods, texnew which is identical to new except it has a different view that redirects to the other new method: texcreate, which uses helper methods to extract the problems and steps (using a series of regexes), tries to create them, and flashes somewhat informative error messages if something goes wrong.

The thing is, I keep on reading that we're really not supposed to be doing a bunch of stuff in the controller, and we should favor doing things in the model instead. Virtual attributes might be the right idea for taking in a text field and processing it to create a single problem, but I can't figure out how to make it work for multiple problems, or how to generate any sort of error messages if so开发者_如何学Cmething goes wrong somewhere along the way.

Is there some better/more idiomatic way to do this?

You don't really need virtual attributes for this if all your relationships are setup properly. You can use the new rails3 nested attributes. There is a good article on them here. This will allow you to rely more on model validation logic and keep the lean controller fat model idiom that rails encourages.