# Declare controller method as helper
class TodoController
  helper_method :login?

  def login?
  end
end

# Using in view (*.html.slim)
- if login?
 = render 'Logout'

# helpers.helper_method
class TodoController
  def show
    message = "#{helpers.helper_method}"
  end
end

class Test
  def show_name # Or: def show_name(&block)
    p 'top'
    yield # Or: block.call
    p 'bottom'
  end
end

a = Test.new
a.show_name do
  p 'middle'
end

module Test
  class << self
    attr_accessor :configuration
  end

  def self.configure
    self.configuration ||= Configuration.new
    yield(configuration)
  end

  class Configuration
    attr_accessor :name
  end
end

Test.configure do |config|
  config.name = 'quyen'
end

p Test.configuration
#<Test::Configuration:0x007f9c8507acc8 @name="quyen">

class ActiveRecord
  def self.has_many(source)
    # def comments
    # end
    define_method(source) do
      p '#{source} method created'
    end
  end
end

class Post < ActiveRecord
  has_many :comments
  has_many :reviews
end

post = Post.new
post.comments