Perfect decorators with Draper

1 min read rails

Draper gives you a great way to decorate your ActiveRecord objects. But what is even better is that it allows you to do that transparently.

Say we have an Article model for our blog.

class Article < ActiveRecord::Base
  extend FriendlyId

  friendly_id :title, use: [:slugged, :finders, :history]

  validates :title, :slug, :body, presence: true

  scope :latest, -> { last(5) }
end

Adding new article decorator

Additionally, we add a new decorator which will allow us to render the body as Markdown.

class ArticleDecorator < Draper::Decorator
  delegate_all

  def markdown_body
    MarkdownService.call(body)
  end
end

Now thanks to Draper’s built in helpers, we can transparently decorate all our objects with decorates_assigned which gives us new helper:

class ArticlesController < ApplicationController
  decorates_assigned :articles, :article

  def index
    @articles = Article.all.page(params[:page])
  end

  def show
    @article = Article.friendly.find(params['article_slug'])
  end
end

decorates_assigned will decorate both @articles and @article for us under the articles and article helper methods defined autmatically.

In the view we can do:

h1= article.title
= article.markdown_body

It saves us from manually specifying @article.decorate or calling ArticleDecorator.decorate(@article).

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