Rails Best Practices ihower@gmail.com 張文鈿
2009/10 As this slide writing, the current Rails version is 2.3.4

Who am I ? •
張文鈿 a.k.a. ihower • http://ihower.tw • http://twitter.com/ihower • http://github.com/ihower • 來自台灣新竹 (Hsinchu,Taiwan)

Ruby Taiwan
http://ruby.tw

Agenda • Concept: What’s good
code? • Move Code from Controller to Model • RESTful best practices • Model best practices • Controller best practices • View best practices

Warning! you should have testing
before modify! 本次演講雖沒有提及測試， 但在修改重構程式前， 應有好的測試， 以確保程式於修改後執行無誤。

Best Practice Lesson 0:
Concepts

Why best practices? • Large
& complicated application 日漸複雜的程式 • Team & different coding style 團隊開發

Your code become... • 僵硬
(Rigidity)：難以修改，每改一處牽一髮動全身 • 脆弱 (Fragility)：一旦修改，別的無關地方也炸到 • 固定 (Immobility)：難以分解，讓程式再重用 • 黏滯 (Viscosity)：彈性不夠，把事情做對比做錯還難 • 不需要的複雜度 (Needless Complexity)：過度設計沒 直接好處的基礎設施 • 不需要的重複 (Needless Repetition)：相同概念的程 式碼被複製貼上重複使用 • 晦澀 (Opacity)：難以閱讀，無法了解意圖 出自 Agile Software Development: Principles, Patterns, and Practices 一書

We need good code:
我們需要好程式

What’s Good code? • Readability
易讀，容易了解 • Flexibility 彈性，容易擴充 • Effective 效率，撰碼快速 • Maintainability 維護性，容易找到問題 • Consistency 一致性，循慣例無需死背 • Testability 可測性，元件獨立容易測試

So,What we can do?
來開始學幾招吧

Best Practice Lesson 1: Move
code from Controller to Model action code 超過15行請注意 http://weblog.jamisbuck.org/2006/10/18/skinny-controller-fat-model

1.Move finder to named_scope class
PostsController < ApplicationController def index @public_posts = Post.find(:all, :conditions => { :state => 'public' }, :limit => 10, :order => 'created_at desc') @draft_posts = Post.find(:all, :conditions => { :state => 'draft' }, :limit => 10, :order => 'created_at desc') end end Before

class UsersController < ApplicationController def
index @published_post = Post.published @draft_post = Post.draft end end class Post < ActiveRecord::Base named_scope :published, :conditions => { :state => 'published' }, :limit => 10, :order => 'created_at desc') named_scope :draft, :conditions => { :state => 'draft' }, :limit => 10, :order => 'created_at desc') end 1.Move finder to named_scope After

2. Use model association class
PostsController < ApplicationController def create @post = Post.new(params[:post]) @post.user_id = current_user.id @post.save end end Before

class PostsController < ApplicationController def
create @post = current_user.posts.build(params[:post]) @post.save end end class User < ActiveRecord::Base has_many :posts end 2. Use model association After

class PostsController < ApplicationController def
edit @post = Post.find(params[:id) if @post.current_user != current_user flash[:warning] = 'Access denied' redirect_to posts_url end end end 3. Use scope access 不必要的權限檢查 Before

class PostsController < ApplicationController def
edit # raise RecordNotFound exception (404 error) if not found @post = current_user.posts.find(params[:id) end end After 3. Use scope access 找不到自然會丟例外

4.Add model virtual attribute <%
form_for @user do |f| %> <%= text_filed_tag :full_name %> <% end %> class UsersController < ApplicationController def create @user = User.new(params[:user) @user.first_name = params[:full_name].split(' ', 2).first @user.last_name = params[:full_name].split(' ', 2).last @user.save end end Before

4.Add model virtual attribute class
User < ActiveRecord::Base def full_name [first_name, last_name].join(' ') end def full_name=(name) split = name.split(' ', 2) self.first_name = split.first self.last_name = split.last end end example code from http://railscasts.com/episodes/16-virtual-attributes After

<% form_for @user do |f|
%> <%= f.text_field :full_name %> <% end %> class UsersController < ApplicationController def create @user = User.create(params[:user) end end example code from http://railscasts.com/episodes/16-virtual-attributes After

5. Use model callback <%
form_for @post do |f| %> <%= f.text_field :content %> <%= check_box_tag 'auto_tagging' %> <% end %> class PostController < ApplicationController def create @post = Post.new(params[:post]) if params[:auto_tagging] == '1' @post.tags = AsiaSearch.generate_tags(@post.content) else @post.tags = "" end @post.save end end Before

5. Use model callback class
Post < ActiveRecord::Base attr_accessor :auto_tagging before_save :generate_taggings private def generate_taggings return unless auto_tagging == '1' self.tags = Asia.search(self.content) end end After

<% form_for :note, ... do
|f| %> <%= f.text_field :content %> <%= f.check_box :auto_tagging %> <% end class PostController < ApplicationController def create @post = Post.new(params[:post]) @post.save end end After

6. Replace Complex Creation with
Factory Method class InvoiceController < ApplicationController def create @invoice = Invoice.new(params[:invoice]) @invoice.address = current_user.address @invoice.phone = current_user.phone @invoice.vip = ( @invoice.amount > 1000 ) if Time.now.day > 15 @invoice.delivery_time = Time.now + 2.month else @invoice.delivery_time = Time.now + 1.month end @invoice.save end end Before

6. Replace Complex Creation with
Factory Method class Invoice < ActiveRecord::Base def self.new_by_user(params, user) invoice = self.new(params) invoice.address = user.address invoice.phone = user.phone invoice.vip = ( invoice.amount > 1000 ) if Time.now.day > 15 invoice.delivery_time = Time.now + 2.month else invoice.delivery_time = Time.now + 1.month end end end After

class InvoiceController < ApplicationController def
create @invoice = Invoice.new_by_user(params[:invoice], current_user) @invoice.save end end After

7. Move Model Logic into
the Model class PostController < ApplicationController def publish @post = Post.find(params[:id]) @post.update_attribute(:is_published, true) @post.approved_by = current_user if @post.create_at > Time.now - 7.days @post.popular = 100 else @post.popular = 0 end redirect_to post_url(@post) end end Before

7. Move Model Logic into
the Model class Post < ActiveRecord::Base def publish self.is_published = true self.approved_by = current_user if self.create_at > Time.now-7.days self.popular = 100 else self.popular = 0 end end end After

class PostController < ApplicationController def
publish @post = Post.find(params[:id]) @post.publish redirect_to post_url(@post) end end After

8. model.collection_model_ids (many-to-many) class User
< ActiveRecord::Base has_many :user_role_relationship has_many :roles, :through => :user_role_relationship end class UserRoleRelationship < ActiveRecord::Base belongs_to :user belongs_to :role end class Role < ActiveRecord::Base end

<% form_for @user do |f|
%> <%= f.text_field :email %> <% for role in Role.all %> <%= check_box_tag 'role_id[]', role.id, @user.roles.include?(role) %> <%= role.name %> <% end %> <% end %> class User < ApplicationController def update @user = User.find(params[:id]) if @user.update_attributes(params[:user]) @user.roles.delete_all (params[:role_id] || []).each { |i| @user.roles << Role.find(i) } end end end Before

<% form_for @user do |f|
%> <% for role in Role.all %> <%= check_box_tag 'user[role_ids][]', role.id, @user.roles.include?(role) <%= role.name %> <% end %> <%= hidden_field_tag 'user[role_ids][]', '' %> <% end %> class User < ApplicationController def update @user = User.find(params[:id]) @user.update_attributes(params[:user]) # 相當於 @user.role_ids = params[:user][:role_ids] end end After

Before 9. Nested Model Forms
(one-to-one) class Product < ActiveRecord::Base has_one :detail end class Detail < ActiveRecord::Base belongs_to :product end <% form_for :product do |f| %> <%= f.text_field :title %> <% fields_for :detail do |detail| %> <%= detail.text_field :manufacturer %> <% end %> <% end %>

class Product < ApplicationController def
create @product = Product.new(params[:product]) @details = Detail.new(params[:detail]) Product.transaction do @product.save! @details.product = @product @details.save! end end end example code from Agile Web Development with Rails 3rd. Before

After 9. Nested Model Forms
(one-to-one) Rails 2.3 new feature class Product < ActiveRecord::Base has_one :detail accepts_nested_attributes_for :detail end <% form_for :product do |f| %> <%= f.text_field :title %> <% f.fields_for :detail do |detail| %> <%= detail.text_field :manufacturer %> <% end %> <% end

After class Product < ApplicationController
def create @product = Product.new(params[:product]) @product.save end end

10. Nested Model Forms (one-to-many)
class Project < ActiveRecord::Base has_many :tasks accepts_nested_attributes_for :tasks end class Task < ActiveRecord::Base belongs_to :project end <% form_for @project do |f| %> <%= f.text_field :name %> <% f.fields_for :tasks do |tasks_form| %> <%= tasks_form.text_field :name %> <% end %> <% end %>

Nested Model Forms before Rails
2.3 ? • Ryan Bates’s series of railscasts on complex forms • http://railscasts.com/episodes/75-complex-forms-part-3 • Recipe 13 in Advanced Rails Recipes book

Best Practice Lesson 2: RESTful
請愛用 RESTful conventions

Why RESTful? RESTful help you
to organize/name controllers, routes and actions in standardization way

class EventsController < ApplicationController def
index end def show end def create end def update end def destroy end end def watch_list end def add_favorite end def invite end def join end def leave end def feeds end def add_comment end def show_comment end def destroy_comment end def edit_comment end def approve_comment end def white_member_list end def black_member_list end def deny_user end def allow_user end def edit_managers end def set_user_as_manager end def set_user_as_member end Before

After class EventsController < ApplicationController
def index; end def show; end end class CommentsControlers < ApplicationController def index; end def create; end def destroy; end end def FavoriteControllers < ApplicationController def create; end def destroy; end end class EventMembershipsControlers < ApplicationController def create; end def destroy; end end

1. Overuse route customizations map.resources
:posts, :member => { :comments => :get, :create_comment => :post, :update_comment => :post, :delete_comment => :post } Before

1. Overuse route customizations Find
another resources map.resources :posts do |post| post.resources :comments end After

Suppose we has a event
model... class Event < ActiveRecord::Base has_many :attendee has_one :map has_many :memberships has_many :users, :through => :memberships end

Can you answer how to
design your resources ? • manage event attendees (one-to-many) • manage event map (one-to-one) • manage event memberships (many-to-many) • operate event state: open or closed • search events • sorting events • event admin interface

Learn RESTful design my slide
about restful: http://www.slideshare.net/ihower/practical-rails2-350619

2. Needless deep nesting 過度設計:
Never more than one level Before map.resources :posts do |post| post.resources :comments do |comment| comment.resources :favorites end end <%= link_to post_comment_favorite_path(@post, @comment, @favorite) %>

After map.resources :posts do |post|
post.resources :comments end map.resources :comments do |comment| comment.resources :favorites end <%= link_to comment_favorite_path(@comment, @favorite) %> 2. Needless deep nesting 過度設計: Never more than one level

3. Not use default route
Before map.resources :posts, :member => { :push => :post } map.connect ':controller/:action/:id' map.connect ':controller/:action/:id.:format'

3. Not use default route
After map.resources :posts, :member => { :push => :post } #map.connect ':controller/:action/:id' #map.connect ':controller/:action/:id.:format' map.connect 'special/:action/:id', :controller => 'special'

Best Practice Lesson 3:
Model

1. Keep Finders on Their
Own Model class Post < ActiveRecord::Base has_many :comments def find_valid_comments self.comment.find(:all, :conditions => { :is_spam => false }, :limit => 10) end end class Comment < ActiveRecord::Base belongs_to :post end class CommentsController < ApplicationController def index @comments = @post.find_valid_comments end end Before

1. Keep Finders on Their
Own Model class Post < ActiveRecord::Base has_many :comments end class Comment < ActiveRecord::Base belongs_to :post named_scope :only_valid, :conditions => { :is_spam => false } named_scope :limit, lambda { |size| { :limit => size } } end class CommentsController < ApplicationController def index @comments = @post.comments.only_valid.limit(10) end end After

2. Love named_scope class PostController
< ApplicationController def search conditions = { :title => "%#{params[:title]}%" } if params[:title] conditions.merge!{ :content => "%#{params[:content]}%" } if params[:content] case params[:order] when "title" : order = "title desc" when "created_at" : order = "created_at" end if params[:is_published] conditions.merge!{ :is_published => true } end @posts = Post.find(:all, :conditions => conditions, :order => order, :limit => params[:limit]) end end Before example code from Rails Antipatterns book

2. Love named_scope After class
Post < ActiveRecord::Base named_scope :matching, lambda { |column, value| return {} if value.blank? { :conditions => ["#{column} like ?", "%#{value}%"] } } named_scope :order, lambda { |order| { :order => case order when "title" : "title desc" when "created_at" : "created_at" end } } end

After class PostController < ApplicationController
def search @posts = Post.matching(:title, params[:title]) .matching(:content, params[:content]) .order(params[:order]) end end

3. the Law of Demeter
class Invoice < ActiveRecord::Base belongs_to :user end <%= @invoice.user.name %> <%= @invoice.user.address %> <%= @invoice.user.cellphone %> Before

3. the Law of Demeter
class Invoice < ActiveRecord::Base belongs_to :user delegate :name, :address, :cellphone, :to => :user, :prefix => true end <%= @invoice.user_name %> <%= @invoice.user_address %> <%= @invoice.user_cellphone %> After

4. DRY: Metaprogramming class Post
< ActiveRecord::Base validate_inclusion_of :status, :in => ['draft', 'published', 'spam'] def self.all_draft find(:all, :conditions => { :status => 'draft' } end def self.all_published find(:all, :conditions => { :status => 'published' } end def self.all_spam find(:all, :conditions => { :status => 'spam' } end def draft? self.stats == 'draft' end def published? self.stats == 'published' end def spam? self.stats == 'spam' end end Before

4. DRY: Metaprogramming class Post
< ActiveRecord::Base STATUSES = ['draft', 'published', 'spam'] validate_inclusion_of :status, :in => STATUSES class << self STATUSES.each do |status_name| define_method "all_#{status}" do find(:all, :conditions => { :status => status_name } end end end STATUSES.each do |status_name| define_method "#{status_name}?" do self.status == status_name end end end After

Breaking Up Models 幫 Model
減重

5. Extract into Module class
User < ActiveRecord::Base validates_presence_of :cellphone before_save :parse_cellphone def parse_cellphone # do something end end Before

# /lib/has_cellphone.rb module HasCellphone def
self.included(base) base.validates_presence_of :cellphone base.before_save :parse_cellphone base.send(:include,InstanceMethods) base.send(:extend, ClassMethods) end module InstanceMethods def parse_cellphone # do something end end module ClassMethods end end After

class User < ActiveRecord::Base include
HasCellphone end After

6. Extract to composed class
Before # == Schema Information # address_city :string(255) # address_street :string(255) class Customer < ActiveRecord::Base def adddress_close_to?(other_customer) address_city == other_customer.address_city end def address_equal(other_customer) address_street == other_customer.address_street && address_city == other_customer.address_city end end

After 6. Extract to composed
class (value object) class Customer < ActiveRecord::Base composed_of :address, :mapping => [ %w(address_street street), %w(address_city city) ] end class Address attr_reader :street, :city def initialize(street, city) @street, @city = street, city end def close_to?(other_address) city == other_address.city end def ==(other_address) city == other_address.city && street == other_address.street end end example code from Agile Web Development with Rails 3rd.

7. Use Observer class Project
< ActiveRecord::Base after_create :send_create_notifications private def send_create_notifications self.members.each do |member| ProjectNotifier.deliver_notification(self, member) end end end Before

class Project < ActiveRecord::Base #
nothing here end # app/observers/project_notification_observer.rb class ProjectNotificationObserver < ActiveRecord::Observer observe Project def after_create(project) project.members.each do |member| ProjectMailer.deliver_notice(project, member) end end end 7. Use Observer After

Best Practice Lesson 4:
Migration

1. Isolating Seed Data Before
class CreateRoles < ActiveRecord::Migration def self.up create_table "roles", :force => true do |t| t.string :name end ["admin", "author", "editor","account"].each do |name| Role.create!(:name => name) end end def self.down drop_table "roles" end end

1. Isolating Seed Data After
# /db/seeds.rb (Rails 2.3.4) ["admin", "author", "editor","account"].each do |name| Role.create!(:name => name) end rake db:seed

After # /lib/tasks/dev.rake (before Rails
2.3.4) namespace :dev do desc "Setup seed data" task :setup => :environment do ["admin", "author", "editor","account"].each do |name| Role.create!(:name => name) end end end rake dev:setup

2. Always add DB index
class CreateComments < ActiveRecord::Migration def self.up create_table "comments", :force => true do |t| t.string :content t.integer :post_id t.integer :user_id end end def self.down drop_table "comments" end end Before

2. Always add DB index
class CreateComments < ActiveRecord::Migration def self.up create_table "comments", :force => true do |t| t.string :content t.integer :post_id t.integer :user_id end add_index :comments, :post_id add_index :comments, :user_id end def self.down drop_table "comments" end end After

Best Practice Lesson 5:
Controller

1. Use before_filter class PostController
< ApplicationController def show @post = current_user.posts.find(params[:id] end def edit @post = current_user.posts.find(params[:id] end def update @post = current_user.posts.find(params[:id] @post.update_attributes(params[:post]) end def destroy @post = current_user.posts.find(params[:id] @post.destroy end end Before

1. Use before_filter class PostController
< ApplicationController before_filter :find_post, :only => [:show, :edit, :update, :destroy] def update @post.update_attributes(params[:post]) end def destroy @post.destroy end protected def find_post @post = current_user.posts.find(params[:id]) end end After

2. DRY Controller class PostController
< ApplicationController def index @posts = Post.all end def show @post = Post.find(params[:id) end def new @post = Post.new end def create @post.create(params[:post] redirect_to post_path(@post) end end Before def edit @post = Post.find(params[:id) end def update @post = Post.find(params[:id) @post.update_attributes(params[:post]) redirect_to post_path(@post) end def destroy @post = Post.find(params[:id) @post.destroy redirect_to posts_path end

After 2. DRY Controller http://github.com/josevalim/inherited_resources
class PostController < InheritedResources::Base # magic!! nothing here! end

After 2. DRY Controller class
PostController < InheritedResources::Base # if you need customize redirect url def create create! do |success, failure| seccess.html { redirect_to post_url(@post) } failure.html { redirect_to root_url } end end end

• You lose intent and
readability • Deviating from standards makes it harder to work with other programmers • Upgrading rails DRY Controller Debate!! 小心走火入魔 from http://www.binarylogic.com/2009/10/06/discontinuing-resourcelogic/

Best Practice Lesson 6:
View

最重要的守則：
Never logic code inViews

1. Move code into controller
<% @posts = Post.find(:all) %> <% @posts.each do |post| %> <%=h post.title %> <%=h post.content %> <% end %> Before class PostsController < ApplicationController def index @posts = Post.find(:all) end end After

2. Move code into model
<% if current_user && (current_user == @post.user || @post.editors.include?(current_user) %> <%= link_to 'Edit this post', edit_post_url(@post) %> <% end %> <% if @post.editable_by?(current_user) %> <%= link_to 'Edit this post', edit_post_url(@post) %> <% end %> class Post < ActiveRecord::Base def ediable_by?(user) user && ( user == self.user || self.editors.include?(user) end end Before After

3. Move code into helper
<%= select_tag :state, options_for_select( [[t(:draft),"draft" ], [t(:published),"published"]], params[:default_state] ) %> Before After <%= select_tag :state, options_for_post_state(params[:default_state]) %> # /app/helpers/posts_helper.rb def options_for_post_state(default_state) options_for_select( [[t(:draft),"draft" ],[t(:published),"published"]], default_state ) end

4. Replace instance variable with
local variable <%= render :partial => "sidebar" %> <%= render :partial => "sidebar", :locals => { :post => @post } %> Before After class Post < ApplicationController def show @post = Post.find(params[:id) end end

5. Use Form Builder <%
form_for @post do |f| %> <p> <%= f.label :title, t("post.title") %> <br> <%= f.text_field :title %> </p> <p> <%= f.label :content %> <br> <%= f.text_area :content, :size => '80x20' %> </p> <p> <%= f.submit t("submit") %> </p> <% end %> Before

5. Use Form Builder After
<% my_form_for @post do |f| %> <%= f.text_field :title, :label => t("post.title") %> <%= f.text_area :content, :size => '80x20', :label => t("post.content") %> <%= f.submit t("submit") %> <% end %>

module ApplicationHelper def my_form_for(*args, &block)
options = args.extract_options!.merge(:builder => LabeledFormBuilder) form_for(*(args + [options]), &block) end end class MyFormBuilder < ActionView::Helpers::FormBuilder %w[text_field text_area].each do |method_name| define_method(method_name) do |field_name, *args| @template.content_tag(:p, field_label(field_name, *args) + "<br />" + field_error(field_name) + super) end end def submit(*args) @template.content_tag(:p, super) end end After

6. Organize Helper files #
app/helpers/user_posts_helper.rb # app/helpers/author_posts_helper.rb # app/helpers/editor_posts_helper.rb # app/helpers/admin_posts_helper.rb class ApplicationController < ActionController::Base helper :all # include all helpers, all the time end # app/helpers/posts_helper.rb Before After

7. Learn Rails Helpers •
Learn content_for and yield • Learn how to pass block parameter in helper • my slide about helper: http://www.slideshare.net/ihower/building-web-interface-on-rails • Read Rails helpers source code • /actionpack-x.y.z/action_view/helpers/*

Best Practice Lesson 7: Code
Refactoring

We have Ruby edition now!!
Must read it!

Reference: 參考網頁: http://weblog.jamisbuck.org/2006/10/18/skinny-controller-fat-model http://www.matthewpaulmoore.com/ruby-on-rails-code-quality-checklist http://www.chadfowler.com/2009/4/1/20-rails-development-no-no-s
參考資料: Pragmatic Patterns of Ruby on Rails 大場寧子 Advanced Active Record Techniques Best Practice Refactoring Chad Pytel RefactoringYour Rails Application RailsConf 2008 The Worst Rails CodeYou've Ever Seen Obie Fernandez Mastering Rails Forms screencasts with Ryan Bates 參考書籍: Agile Software Development: Principles, Patterns, and Practices AWDwR 3rd The Rails Way 2nd. Advanced Rails Recipes Refactoring Ruby Edition Ruby Best Practices Enterprise Rails Rails Antipatterns Rails Rescue Handbook Code Review (PeepCode) Plugin Patterns (PeepCode)

More best practices: • Rails
Performance http://www.slideshare.net/ihower/rails-performance • Rails Security http://www.slideshare.net/ihower/rails-security-3299368

感謝聆聽，請多指教。
Thank you.