my lecture on 18th Nov.

0.oop.rb

class Human # => design
  def say_hello(name)
    'hello' + name
  end
end

@human = Human.new # instance
@human.say_hello('David')
#=> 'hello David'

controller.rb

class UsersController < ApplicationController
  before_filter :ensure_login

  def show
    @main_displays = MainDisplay.limit(10)

    @main_displays.remain_more_than!(0.1)
  end

  private # Put the following code into ApplicationController

  def ensure_login
    @login_user = User.find(params[:user_id]

    unless @login_user.present?
      redirect_to login_path
    end
  end
end

helper.rb

# helper
def message_if_no_record(displays)
  if displays.count == 0
    'No display found.'
  end
end

model.rb

# model
def remain_more_than!(rate)
  @main_displays.select! {|main_display| main_diplay.rate > rate }
end

view.rb

%table
  = message_if_no_record(@main_displays)
  - @main_displays.each do |main_display|
    %tr
      %td
        = main_diplay.tile