dashboard_controller.rb

class DashboardController < ApplicationController
  before_filter :require_user
  
  def index
    @feed_items = FeedItem.followed_by(current_user.id).
                          includes(:post).paginate(:page => params[:page])
    @page_title = "#{APP_CONFIG['site_name']} | Dashboard"
  end
  
end

feed_item.rb

class FeedItem < ActiveRecord::Base
  attr_accessible *%W[
    actor_id
    actor
    subject
    secondary_subject
    event_type
  ]
  
  belongs_to :subject, :polymorphic => true
  belongs_to :secondary_subject, :polymorphic => true
  belongs_to :actor, :class_name => 'User'
  
  belongs_to :post, :class_name => "Post", :foreign_key  => "subject_id"
  
  default_scope :order => 'feed_items.created_at DESC'
  
  scope :followed_by, lambda { |user_id| {
    :joins => "INNER JOIN \"followings\" ON followings.feeder_id = feed_items.actor_id",
    :conditions => ['followings.follower_id = ?', user_id],
    :select => 'DISTINCT feed_items.*' 
  }}
  
end

following.rb

class Following < ActiveRecord::Base
  attr_accessible *%W[
    feeder
    feeder_id
    follower
    follower_id
  ]
  
  belongs_to :feeder, :class_name => 'User'
  belongs_to :follower, :class_name => 'User'
  
  validates_presence_of :feeder_id, :follower_id
  validates_uniqueness_of :follower_id, :scope => :feeder_id
end

post.rb

class Post < ActiveRecord::Base
  attr_accessible *%W[
    body
  ]
    
  belongs_to :author, :class_name => 'User'
  belongs_to :project
  has_many :feed_items, :as => :subject, :dependent => :destroy
  
  after_create  :generate_feed_item

protected
  
  def generate_feed_item
    FeedItem.create({
      :event_type => "new_post",
      :actor => self.author,
      :subject => self, 
      :secondary_subject => self.project
    })
  end
end

user.rb

class User < ActiveRecord::Base

  has_many :feeder_followings, 
            :foreign_key => 'follower_id',
            :class_name => 'Following'
  has_many :feeders, :through => :feeder_followings
  has_many :follower_followings,
            :foreign_key => 'feeder_id',
            :class_name => 'Following'
  has_many :followers, :through => :follower_followings
  
  # following
  
  def follow!(feeder)
    self.feeders << feeder
  end
  
  def unfollow!(feeder)
    if f = follows?(feeder)
      f.destroy
    end
  end
  
  def follows?(feeder)
    self.feeder_followings.where(:feeder_id => feeder.id).first
  end
  
end