Presenter Objects

a.k.a. Decorators / View objects / View models

Version #1

http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/

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

Version #2

• https://github.com/amatsuda/active_decorator
• https://speakerdeck.com/blowmage/presenters-and-decorators-a-code-tour

# app/models/user.rb
class User < ActiveRecord::Base
  # first_name:string last_name:string website:string
end

# app/decorators/user_decorator.rb
module UserDecorator
  def full_name
    "#{first_name} #{last_name}"
  end

  def link
    link_to full_name, website
  end
end

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  def index
    @users = User.all
  end
end

<%# app/views/users/index.html.erb %>
<% @users.each do |user| %>
  <%= user.link %><br>
<% end %>

Version #3

• https://github.com/amatsuda/active_decorator
• https://speakerdeck.com/blowmage/presenters-and-decorators-a-code-tour

class AuthorSummary
  def initialize(author)
    @author = author
  end
  def published_count
    @author.posts.published.count +
    @author.videos.published.count
  end
  def draft_count
    @author.posts.unpublished.count +
    @author.videos.unpublished.count
  end
  def approval_count
    if @author.admin?
      @author.organization.posts.unapproved.count
    else
      0
    end
  end
end

<% summary = AuthorSummary.new(current_user) %>