Passing data between controllers with the session RESTfully

Question

I'm using a hideous pattern in my code and I know there must be a better way to do this. Help me rethink what I'm doing.

My website is a kind of discussion forum. All replies to discussions are done on the DiscussionsController#show page, inline.

Some replies are invalid, though - for example, if you try and post a reply that has no text in it, it returns you to DiscussionsController#show with an error message.

Here's a brief outline of how I've implemented this workflow:

1. User goes to DiscussionsController#show. This template has a reply form on it. There is no explicit RepliesController#new action.
2. User submits reply form, which is POSTed to replies_path and handled in RepliesController#create.
3. RepliesController#create is unable to save the reply because it's invalid (validates_length_of in Reply invalidates the object).
4. RepliesController#create puts the reply object in session[:new_reply] and redirects to the discussion_path the user came from.
5. DiscussionsController#show handles the session object...

Like so:

if session[:new_reply]
  @new_reply = session[:new_reply]
  session.delete(:new_reply)
end

And now show.html.erb has a newly-regenerated @new_reply object to inspect for errors.

There's something obviously wrong with this - you shouldn't store entire objects inside of the session. But since the Reply object we attempted to save in RepliesController#create is never saved, how do I persist it between controller action calls?

Or if there's a larger design solution, feel free to share it. This is so ugly it's hurting me. Thanks.

Answer 1

How about instead of redirecting, do render :action => "discussions/show" instead. I was going to say you'd have to set up the @discussion variable too, but this should be done since replies are nested resources inside of discussions, right?

Answer 2

Instead of the session, I would store the reply in the flash, which is good for passing messages/objects across an action.

The controller would simply store the reply in the flash if it wasn't valid and redirect:

if @reply.save
   ...
else
   flash[:reply] = @reply
end

And your form logic on the discussions/show page would need to be a bit smarter and grab the reply in the flash or the new one (which I assume you are creating in the discussions/show action):

form_for(flash[:reply] || @reply) do
  ...
end

Answer 3

I would say that the way you're doing it is reasonable. Not the cleanest but it is RESTful.

Radar's suggestion is great but in the current version of Rails, using render :action => "discussions/show" doesn't create the correct behavior, at least in my attempts, which have been without nested resources routing. Using render :controller => "discussions", :action => "show" yields another behavior that isn't what the poster is looking for.