Filtering results through URL (e.g. new?forum_id=3)

Is there a special code you have to place in the routes so filtering
results through the URL works?

For example, Ruby Forum does it with:

http://www.ruby-forum.com/topic/new?forum_id=3
http://www.ruby-forum.com/topic/new?forum_id=5
http://www.ruby-forum.com/topic/new?forum_id=7
etc.

Any ideas?

Hi Bob,

It seems that the example you gave may be doing something different
that what you describe. I believe the forum_id will be used as a value
in a new topic form, not as a "filter" for a list of topics.

You might look at this: http://api.rubyonrails.org/classes/ActionController/Resources.html#M000696
Specifically the part about routing association.

If you wanted to "filter" a list of topics by forum_id you might do
something like the following:
# routes.rb
map.resources :forums do |forums|
  forums.resources :topics
end

This would generate routes like forum_topics and new_forum_topic so
you could call the following in your controllers & views:
# some_view.html.erb
<%= link_to "click here to see #{@my_forum.name} topics",
forum_topics_path(@my_forum) %>

This would result in a link to /forums/7/topics where @my_forum's id
is 7.

For a complete list of routes you've defined try this in your command
line:
$ rake routes

When GETing the path above, your topics_controller index action will
be called. In that method you'll need to look for params[:forum_id]
when finding your list of topics for the desired forum:
# topics_controller
def index
  if params[:forum_id]
    #find topics belonging to a specified forum
    @forum = Forum.find(params[:forum_id])
    @topics = @forum.topics
  else
    # find all topics
    @topics = Topic.find(:all)
  end
  ...
end

Good luck.

*untested code examples

Really appreciate the help, gsterndale! =)

Very detailed. Thank you so much!