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    <p>When I've <a href="http://www.lonelyplanet.com/members/madlep">done this before</a> I've managed it by having a denormalised <code>UserActivity</code> model or similar with a <code>belongs_to</code> polymorphic association to an <code>ActivitySource</code> - which can be any of the types of content that you want to display (posts, comments, up votes, likes, whatever...).</p> <p>Then when any of the entities to be displayed are created, you have an <code>Observer</code> that fires and creates a row in the <code>UserActivity</code> table with a link to the record.</p> <p>Then to display the list, you just query on <code>UserActivity</code> ordering by <code>created_at</code> descending, and then navigate through the polymorphic <code>activity_source</code> association to get the content data. You'll then need some smarts in your view templates to render comments and posts and whatever else differently though.</p> <p>E.g. something like...</p> <p>user_activity.rb:</p> <pre><code>class UserActivity &lt; ActiveRecord::Base belongs_to :activity_source, :polymorphic =&gt; true # awesomeness continues here... end </code></pre> <p>comment.rb (post/whatever)</p> <pre><code>class Comment &lt; ActiveRecord::Base # comment awesomeness here... end </code></pre> <p>activity_source_observer.rb</p> <pre><code>class ActivitySourceObserver &lt; ActiveRecord::Observer observe :comment, :post def after_create(activity_source) UserActivity.create!( :user =&gt; activity_source.user, :activity_source_id =&gt; activity_source.id, :activity_source_type =&gt; activity_source.class.to_s, :created_at =&gt; activity_source.created_at, :updated_at =&gt; activity_source.updated_at) end def before_destroy(activity_source) UserActivity.destroy_all(:activity_source_id =&gt; activity_source.id) end end </code></pre>
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    1. COOne problem with this is that when a model is destroyed, you're destroying its associated activities rather than creating an activity for the destruction. Imagine an activity feed like github's; when you create a repository, that gets posted to your feed. When you delete a repository your feed shows that you deleted a repository.
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    2. CO@bratsche i feel like that is an edge case. this is an inherently messy/complicated thing to build, for my purposes, if someone deletes a record, I actually DO want the feed items removed.
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