Presenters from http://habrahabr.ru/post/266761/

app__helpers__application_helper.rb

module ApplicationHelper
  def present(model)
    return if model.blank?
    klass = "#{model.class}Presenter".constantize
    presenter = klass.new(model, self)
    yield(presenter) if block_given?
    presenter
  end
end

app__presenters__base_presenter.rb

class BasePresenter < Delegator
  attr_reader :model, :h
  alias_method :__getobj__, :model

  def initialize(model, view_context)
    @model = model
    @h = view_context
  end

  def inspect
    "#<#{self.class} model: #{model.inspect}>"
  end
end

app__presenters__post_presenter.rb

class PostPresenter < BasePresenter
  def to_link
    h.link_to model.to_s, model
  end

  def content
    h.markdown model.content
  end

  # оборачиваем связь
  def comments
    model.comments.map { |comment| h.present comment }
  end
end

app__views__posts__index.slim

- @posts.each do |post|
  .post
    - present(post) do |post_presenter|
      h2 = post_presenter.title
      = post_presenter.content