BWeave Ramblings, maybe, when I get around to it.

ActiveRecord::Observer

15 May 2021

TIL ActiveRecord::Observer is a thing. You can use it to pull AR model callbacks out into dedicated classes. This seems useful if you’ve got a handful(s) of related callbacks and need a better way to organize them.

class PostObserver < ActiveRecord::Observer
  def after_create(post)
    Subscribers.send_new_post_notification(post)
  end
end

class CommentObserver < ActiveRecord::Observer
  def after_create(comment)
    Subscribers.send_new_comment_notification(comment)
  end
end

As you might’ve guessed, the class to observe is inferred, so in the case where it can’t be inferred, or multiple classes should be watched, do this.

class AuditObserver < ActiveRecord::Observer
  observe :account, :balance

  def after_update(record)
    AuditTrail.new(record, "UPDATED")
  end
end

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