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65 Common Features:

Activity Feed From Scratch

Episode 70 · July 3, 2015

Learn how to build an activity feed from scratch and how to manage lots of flexible partials



<% @events.each do |event| %>
  <% if lookup_context.template_exists?(event.action, "events/activities", true) %>
    <%= render partial: "events/activities/#{event.action}", locals: {event: event} %>
  <% end %>
<% end %>


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Could you post the source code to this?


Absolutely! Just posted it here:


event.eventable is an instance of a class right


Yep! That's correct. It's actually another model instance but just given the name of "eventable" because it could be of various types of models.


How do we handle deletion dependencies here? E.g. say I setup an event to be trigged on a `comment` creation, or when I upload an image. But what happens when I delete that comment or I delete that image. Ideally, I would like to be able to delete the event that is related to that specific recently deleted comment or image.

What's the best way to do this?


This is a fantastic question. If you setup the reverse dependency and set the dependent destroy option, that will delete the events when you delete the comment.

class Comment
has_many :events, as: :eventable, dependent: :destroy

Ahh perfect. So that covers most use-cases. How do I handle virtual attributes, e.g. 'votes'. So I am using acts_as_votable, which creates a bunch of virtual attributes to indicate when a user has `liked` a `Node`. When that node is deleted, all of those virtual attributes are deleted, so I would like to delete all of those events too.

Do I have to do this manually in an `after_delete :callback` on my `Node` model or is there some other way?


Depending on how that's setup, you might patch the Vote model so that if you created events matched to the vote, you could delete those. You can't really set this up on virtual attributes because you need it attached directly to the records so when things get deleted you can remove the related records.

Fallback I guess the solution just may be in the removal of the Node callback. Or just adding the `dependent: :destroy` on my Node model. Or maybe I just ignore it, given that it is just a like.


Love it keep it up Chris


Hey Chris. Thanks for all the awesome tutorials. If I wanted to add a link to "Unfollow" and delete the event, what would that look like?

It looks like the `lookup_context.template_exists?()` method now requires the prefixes to be an array, or an enumerable that responds to `.map()`, instead of just a string. This was changed as previous versions of Rails (< 3.1) accepted a string prefix. I'm not sure why it works in the episode, since you're using Rails 4; maybe it was a soft deprecation?


Great video, man. I had originally figure out how to do this on my own, and was like, "that's me!" when you mentioned how not to do it. Thanks for showing an alternative to "if activity type is this, show this". I was able to refactor quite a bit of code.

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