vsavkin

def sell_book
  @book = Book.find(params[:id])
  BookSellingService.sell_book(@book)
end

vsavkin

class Post < ActiveRecord::Base
  has_many :comments
  after_create :send_tweet

  def send_tweet
    twitter = Twitter.login(username, password)
    twitter.send_tweet generate_tweet_from_subject(subject)
  end
end

vsavkin

class Post < ActiveRecord::Base
  has_many :comments
end

class TwitterNotification < ActiveRecord::Observer
  observe :post

  def after_create post
    twitter = Twitter.login(username, password)
    twitter.send_tweet generate_tweet_from_subject(post.subject)

vsavkin

class TwitterNotification < ActiveRecord::Observer
  observe :post

  def after_create post
    TwitterService.send_tweet post.subject
  end
end

class TwitterService
  def self.send_tweet subject

vsavkin

class PostsRepository
  def find_by_id id
    ...
  end

  def new_posts_of_author author
    ...
  end

  def save post

vsavkin

module PostsRepository
  def new_posts_of_author author
    ...
  end
end

class Post
  extend PostsRepository
end

vsavkin

class TwitterNotification < ActiveRecord::Observer
  observe :post

  def after_create post
    TwitterService.send_tweet post.subject
  end
end

class TwitterService
  def self.send_tweet subject

vsavkin

class TwitterNotification < ActiveRecord::Observer
  observe :post

  def after_create post
    TwitterService.send_tweet post.subject
  end
end

class TwitterService
  def self.send_tweet subject

vsavkin

module PostsRepository
  def new_posts_of_author author
    ...
  end
end

class Post < ActiveRecord::Base
  extend PostsRepository
end

vsavkin

module PostsRepository
  def new_posts_of_author author
    ...
  end
end

class Post < ActiveRecord::Base
  extend PostsRepository
end