Creating "feeds" from multiple, different Rails models

Question

I'm working on an application that has a few different models (tickets, posts, reports, etc..). The data is different in each model and I want to create a "feed" from all those models that displays the 10 most recent entries across the board (a mix of all the data).

What is the best way to go about this? Should I create a new Feed model and write to that table when a user is assigned a ticket or a new report is posted? We've also been looking at STI to build a table of model references or just creating a class method that aggregates the data. Not sure which method is the most efficient...

Answer 1

Create an Item model that includes the attributes "table_name" and "item_id". Then create a partial for each data type. After you save, let's say, a ticket, create an Item instance:

i = Item.create(:table_name => 'tickets', :item_id => @ticket.id)

In your items_controller:

def index
   @items = Item.find(:all, :order => 'created_on DESC')
end

In views/items/index.erb:

<% @items.each do |item| %>
  <%= render :partial => item.table_name, :locals => {:item => item} %><br />
<% end %>

Answer 2

You can do it one of two ways depending on efficiency requirements.

The less efficient method is to retrieve 10 * N items and sort and reduce as required:

# Fetch 10 most recent items from each type of object, sort by
# created_at, then pick top 10 of those.
@items = [ Ticket, Post, Report ].inject([ ]) do |a, with_class|
  a + with_class.find(:all, :limit => 10, :order => 'created_at DESC')
end.sort_by(&:created_at).reverse[0, 10]

Another method is to create an index table that's got a polymorphic association with the various records. If you're only concerned with showing 10 at a time you can aggressively prune this using some kind of rake task to limit it to 10 per user, or whatever scope is required.