Decorate associated objects

README.md

@@ -65,48 +65,6 @@ end
 <% end %>
 ```
 
-## Decorating associated objects ##
-
-ActiveDecorator *does not* automatically decorate associated objects. We recommend that you pass associated objects to `render` when decorated associated objects are needed.
-
-```ruby
-# app/models/blog_post.rb
-class BlogPost < ActiveRecord::Base
-  # published_at:datetime
-end
-
-# app/models/user.rb
-class User < ActiveRecord::Base
-  has_many :blog_posts
-end
-
-# app/decorators/blog_post_decorator.rb
-module BlogPostDecorator
-  def published_date
-    published_at.strftime("%Y.%m.%d")
-  end
-end
-
-# app/controllers/users_controller.rb
-class UsersController < ApplicationController
-  def index
-    @users = User.all
-  end
-end
-```
-
-```erb
-# app/views/users/index.html.erb
-<% @users.each do |user| %>
-  <%= render partial: "blog_post", locals: { blog_posts: user.blog_posts } %><br>
-<% end %>
-
-# app/views/users/_blog_post.html.erb
-<% blog_posts.each do |blog_post| %>
-  <%= blog_post.published_date %>
-<% end %>
-```
-
 ## Testing
 
 You can test a decorator using your favorite test framework by decorating the model instance with

lib/active_decorator/decorated.rb

@@ -0,0 +1,2 @@
+module ActiveDecorator::Decorated
+end

lib/active_decorator/decorator.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 require 'singleton'
 require 'active_decorator/helpers'
+require 'active_decorator/decorated'
 
 module ActiveDecorator
   class Decorator
@@ -28,13 +29,21 @@ def decorate(obj)
           obj.extend ActiveDecorator::RelationDecoratorLegacy unless obj.is_a? ActiveDecorator::RelationDecoratorLegacy
         end
       else
+        if defined?(ActiveRecord) && obj.is_a?(ActiveRecord::Base) && !obj.is_a?(ActiveDecorator::Decorated)
+          obj.extend ActiveDecorator::Decorated
+        end
+
         d = decorator_for obj.class
         return obj unless d
         obj.extend d unless obj.is_a? d
         obj
       end
     end
 
+    def decorate_association(owner, target)
+      owner.is_a?(ActiveDecorator::Decorated) ? decorate(target) : target
+    end
+
     private
     def decorator_for(model_class)
       return @@decorators[model_class] if @@decorators.key? model_class

lib/active_decorator/monkey/active_record/associations.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+module ActiveDecorator
+  module Monkey
+    module ActiveRecord
+      module Associations
+        module Association
+          def target
+            ActiveDecorator::Decorator.instance.decorate_association(owner, super)
+          end
+        end
+
+        module CollectionAssociation
+          # @see https://github.com/rails/rails/commit/03855e790de2224519f55382e3c32118be31eeff
+          if Rails.version.to_f < 4.1
+            def first_or_last(*args)
+              ActiveDecorator::Decorator.instance.decorate_association(owner, super)
+            end
+          else
+            def first_nth_or_last(*args)
+              ActiveDecorator::Decorator.instance.decorate_association(owner, super)
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/active_decorator/railtie.rb

@@ -28,6 +28,12 @@ class Railtie < ::Rails::Railtie
           ActionMailer::Base.send :include, ActiveDecorator::ViewContext::Filter
         end
       end
+
+      ActiveSupport.on_load :active_record do
+        require 'active_decorator/monkey/active_record/associations'
+        ActiveRecord::Associations::Association.send :prepend, ActiveDecorator::Monkey::ActiveRecord::Associations::Association
+        ActiveRecord::Associations::CollectionAssociation.send :prepend, ActiveDecorator::Monkey::ActiveRecord::Associations::CollectionAssociation
+      end
     end
   end
 end

test/fake_app/app/views/authors/show.html.erb

@@ -1,2 +1,9 @@
 <%= @author.name %>
 <%= @author.capitalized_name %>
+<%= @author.books.first.upcased_title %>
+<%= @author.books[-1].upcased_title %>
+<% if p = @author.publishers.last %><%= p.upcased_name %><% end %>
+<% if p = @author.profile %><%= p.address %><% end %>
+<% if h = @author.profile_history %><%= h.update_date %><% end %>
+<% if m = @author.magazines.first %><%= m.upcased_title %><% end %>
+<% if c = @author.company %><%= c.reverse_name %><% end %>

test/fake_app/app/views/movies/show.html.erb

@@ -1 +1,2 @@
 <%= @movie.name %>
+<% if a = @movie.author %><%= a.reverse_name %><% end %>

test/fake_app/fake_app.rb

@@ -46,13 +46,39 @@ class Application < Rails::Application
 # models
 class Author < ActiveRecord::Base
   has_many :books
+  has_many :publishers, through: :books
+  has_many :movies
+  has_one :profile
+  has_one :profile_history, through: :profile
+  has_and_belongs_to_many :magazines
+  belongs_to :company
 end
 class Book < ActiveRecord::Base
   belongs_to :author
+  belongs_to :publisher
+  accepts_nested_attributes_for :publisher
 end
 class Novel < Book
 end
 class Movie < ActiveRecord::Base
+  belongs_to :author
+end
+class Publisher < ActiveRecord::Base
+  has_many :books
+end
+class Profile < ActiveRecord::Base
+  belongs_to :author
+  has_one :profile_history
+  accepts_nested_attributes_for :profile_history
+end
+class ProfileHistory < ActiveRecord::Base
+  belongs_to :profile
+end
+class Magazine < ActiveRecord::Base
+  has_and_belongs_to_many :authors
+end
+class Company < ActiveRecord::Base
+  has_many :authors
 end
 
 # helpers
@@ -93,6 +119,31 @@ def error
     "ERROR"
   end
 end
+module PublisherDecorator
+  def upcased_name
+    name.upcase
+  end
+end
+module ProfileDecorator
+  def address
+    "secret"
+  end
+end
+module ProfileHistoryDecorator
+  def update_date
+    updated_on.strftime('%Y/%m/%d')
+  end
+end
+module MagazineDecorator
+  def upcased_title
+    title.upcase
+  end
+end
+module CompanyDecorator
+  def reverse_name
+    name.reverse
+  end
+end
 
 # decorator fake
 class MovieDecorator; end
@@ -178,9 +229,15 @@ def thanks(book)
 # migrations
 class CreateAllTables < ActiveRecord::Migration
   def self.up
-    create_table(:authors) {|t| t.string :name}
-    create_table(:books) {|t| t.string :title; t.references :author; t.string :type }
-    create_table(:movies) {|t| t.string :name}
+    create_table(:authors) {|t| t.string :name; t.references :company}
+    create_table(:books) {|t| t.string :title; t.string :type; t.references :author; t.references :publisher }
+    create_table(:profiles) {|t| t.string :address; t.references :author}
+    create_table(:profile_histories) {|t| t.date :updated_on; t.references :profile}
+    create_table(:publishers) {|t| t.string :name}
+    create_table(:movies) {|t| t.string :name; t.references :author}
+    create_table(:magazines) {|t| t.string :title}
+    create_table(:authors_magazines) {|t| t.references :author; t.references :magazine}
+    create_table(:companies) {|t| t.string :name}
   end
 end
 

test/features/association_test.rb

@@ -0,0 +1,36 @@
+require 'test_helper'
+
+class AssociationTest < ActionDispatch::IntegrationTest
+  setup do
+    company = Company.create! name: 'NaCl'
+    @matz = company.authors.create! name: 'matz'
+    @matz.books.create!(
+      title: 'the world of code',
+      publisher_attributes: { name: 'nikkei linux' }
+    )
+    @matz.books.create!(
+      title: 'the ruby programming language',
+      publisher_attributes: { name: "o'reilly" }
+    )
+    @matz.create_profile! address: 'Matsue city, Shimane'
+    @matz.profile.create_profile_history! updated_on: Date.new(2017, 2, 7)
+    @matz.magazines.create! title: 'rubima'
+  end
+
+  test 'decorating associated objects' do
+    visit "/authors/#{@matz.id}"
+    assert page.has_content? 'the world of code'.upcase
+    assert page.has_content? 'the ruby programming language'.upcase
+    assert page.has_content? "o'reilly".upcase
+    assert page.has_content? 'secret'
+    assert page.has_content? '2017/02/07'
+    assert page.has_content? 'rubima'.upcase
+    assert page.has_content? 'NaCl'.reverse
+  end
+
+  test "decorating associated objects that owner doesn't have decorator" do
+    movie = Movie.create! author: @matz
+    visit "/movies/#{movie.id}"
+    assert page.has_content? 'matz'.reverse
+  end
+end