I'm trying to decide what's the best way to build this out. Basically I'm going to observe all kinds of events in the system and create feed items for users based on a number of criteria - "John changed the Status of Job: JUE-923 to active". I'm facing a diliema on how to build the actual FeedItemGenerator part. Below are two ways and how they w…

feed_item_generator.rb

#This works but is maybe not so great.
class FeedItemGenerator
  include ActionView::Helpers

  attr_accessor :feedable
  attr_accessor :user
  attr_accessor :event

  def initialize(feedable, user, event=nil)
    @feedable = feedable
    @user = user
    @event = event
    self.extend CommentFeedItem if feedable.class.name == "Comment"
    self.extend JobFeedItem if feedable.class.name == "Job"
    self.extend TimesheetFeedItem if feedable.class.name == "Timesheet"
  end

  def generate
    fi = FeedItem.new(glyph: glyph, message: feed_item_message, sender_id: user.id, feedable_url: feedable_url)
    Feed.all.each do |feed|
      feed << fi
    end
  end
end

module CommentFeedItem
  def feedable_url
    "#{feedable.commentable.class.name.underscore}/#{feedable.commentable.id}"
  end

  def glyph
    "n"
  end

  def feed_item_message
    "#{user.name} commented on #{feedable.commentable.class.name}: #{feedable.commentable.name}"
  end
end

module JobFeedItem
  def feedable_url
    "#{feedable.class.name.underscore}/#{feedable.id}"
  end

  def glyph
    "k"
  end

  def feed_item_message
    "#{user.name} changed status of #{feedable.class.name}: #{feedable.name} to #{feedable.state.humanize.titleize}"
  end
end

module TimesheetFeedItem
  def feedable_url
    "jobs/#{feedable.job.id}/#{feedable.class.name.underscore}/#{feedable.id}"
  end

  def glyph
    "i"
  end

  def feed_item_message
    "#{sender.full_name} #{event.to_s}d a new timesheet for #{feedable.employee_full_name}."
  end

end

feed_item_generator_subclasses.rb

class FeedItemGenerator
  include ActionView::Helpers

  attr_accessor :feedable
  attr_accessor :user
  attr_accessor :event

  def initialize(feedable, user, event=nil)
    @feedable = feedable
    @user = user
    @event = event
  end

  def generate
    fi = FeedItem.new(glyph: glyph, message: feed_item_message, sender_id: user.id, feedable_url: feedable_url)
    Feed.all.each do |feed|
      feed << fi
    end
  end
end

class CommentFeedItem < FeedItemGenerator
  def feedable_url
    "#{feedable.commentable.class.name.underscore}/#{feedable.commentable.id}"
  end

  def glyph
    "n"
  end

  def feed_item_message
    "#{user.name} commented on #{feedable.commentable.class.name}: #{feedable.commentable.name}"
  end
end

class JobFeedItem < FeedItemGenerator
  def feedable_url
    "#{feedable.class.name.underscore}/#{feedable.id}"
  end

  def glyph
    "k"
  end

  def feed_item_message
    "#{user.name} changed status of #{feedable.class.name}: #{feedable.name} to #{feedable.state.humanize.titleize}"
  end
end

class TimesheetFeedItem < FeedItemGenerator
  def feedable_url
    "jobs/#{feedable.job.id}/#{feedable.class.name.underscore}/#{feedable.id}"
  end

  def glyph
    "i"
  end

  def feed_item_message
    "#{sender.full_name} #{event.to_s}d a new timesheet for #{feedable.employee_full_name}."
  end

end

timesheet_observer.rb

#Using the extending modules method, this is then called in, say, an observer like so:
class TimesheetObserver < ActiveRecord

  def after_create(timesheet)
    FeedItemGenerator.new(timesheet, current_user, :create).generate
  end

end


#Or, using the subclassing method:
class TimesheetObserver < ActiveRecord

  def after_create(timesheet)
    TimesheetFeedItem(timesheet, current_user, :create)
  end

end