class City
  include Virtus.model
  attribute :name, String
end

class Address
  include Virtus.model
  attribute :street,  String
  attribute :zipcode, String
  attribute :city,    City
end

class User
  include Virtus.model
  attribute :name,    String
  attribute :address, Address
end

user = User.new(:address => {
  :street => 'Street 1/2', :zipcode => '12345', :city => { :name => 'NYC' } })

class User
  include Virtus.model
  include ActiveModel::Validations

  validates :name, present: true

  attribute :name,    String
  attribute :address, Address

  def persist
    if valid?
      ...
    end
  end
end

class GeoLocation
  include Virtus.value_object

  values do
    attribute :latitude,  Float
    attribute :longitude, Float
  end
end

class Venue
  include Virtus.value_object

  values do
    attribute :name,     String
    attribute :location, GeoLocation
  end
end

venue = Venue.new(
  :name     => 'Pub',
  :location => { :latitude => 37.160317, :longitude => -98.437500 })

p venue.location.latitude # 37.160317

class AbandonedTrialQuery
  def initialize(relation = Account.scoped)
    @relation = relation
  end

  def find_each(&block)
    @relation.
      where(plan: nil, invites_count: 0).
      find_each(&block)
  end
end

AbandonedTrialQuery.new.find_each do |account|
  account.send_offer_for_support
end

old_accounts = Account.where("created_at < ?", 1.month.ago)
old_abandoned_trials = AbandonedTrialQuery.new(old_accounts)

class Pokemon < ActiveRecord::Base
  scope :with_skill, -> (skill){ joins(:pokemon_skills).
    where("pokemon_skills.name = ?", skill) }
  scope :is_available, -> (date){ joins(:schedules).
    where('schedules.day_of_week = ?', time(date).wday) }-
  scope :with_weakness, -> (weakness){ joins(:pokemon_weakness).
    where("pokemon_weakness.name = ?", weakness) }
end

class PokemonQuery
  def initialize(relation = Pokemon.all)
    @relation = relation.extending(Scopes)
  end

  def search
    @relation
  end

  module Scopes
    def with_skill(skill)
      joins(:pokemon_skills).where("pokemon_skills.name = ?", skill)
    end

    def is_available(date)
      joins(:schedules).where('schedules.day_of_week = ?', time(date).wday)
    end

    def with_weakness(weakness)
      joins(pokemon_weakness).where("pokemon_weakness.name = ?", weakness)
    end
  end
end

PokemonQuery.new.search.with_skill("lightning").with_weakness("water")

class DonutChart
  def initialize(snapshot)
    @snapshot = snapshot
  end

  def cache_key
    @snapshot.id.to_s
  end

  def data
    # pull data from @snapshot and turn it into a JSON structure
  end
end

class ActiveUserPolicy
  def initialize(user)
    @user = user
  end

  def active?
    @user.email_confirmed? &&
    @user.last_login_at > 14.days.ago
  end
end

class FacebookCommentNotifier
  def initialize(comment)
    @comment = comment
  end

  def save
    @comment.save && post_to_wall
  end

private

  def post_to_wall
    Facebook.post(title: @comment.title, user: @comment.author)
  end
end

class CommentsController < ApplicationController
  def create
    @comment = FacebookCommentNotifier.new(Comment.new(params[:comment]))

    if @comment.save
      redirect_to blog_path, notice: "Your comment was posted."
    else
      render "new"
    end
  end
end

class TripReservationsController < ApplicationController
  def create
    reservation = TripReservation.new(params[:trip_reservation])
    trip = Trip.find_by_id(reservation.trip_id)
    agency = trip.agency
    payment_adapter = PaymentAdapter.new(buyer: current_user)
    unless current_user.can_book_from?(agency)
      redirect_to trip_reservations_page, notice: "You're not allowed to book fro\
    m this agency."
    end
    unless trip.has_free_tickets?
      redirect_to trip_reservations_page, notice: "No free tickets available"
    end

    begin
      receipt = payment_adapter.pay(trip.price)
      reservation.receipt_id = receipt.uuid
    unless reservation.save
      logger.info "Failed to save reservation: #{reservation.errors.inspect}"
      redirect_to trip_reservations_page, notice: "Reservation error."
    end
    redirect_to trip_reservations_page(reservation), notice: "Thank your for yo\
    ur reservation!"
    rescue PaymentError
      logger.info "User #{current_user.name} failed to pay for a trip #{trip.name\
      Extracting a service object 34
      }: #{$!.message}"
      redirect_to trip_reservations_page, notice: "Payment error."
    end
  end
end

• http://helabs.com.br/blog/2014/01/18/turn-simple-with-query-objects/
• http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
• http://rails-refactoring.com/
• http://datamapper.org