As developers worldwide have adopted the Ruby on Rails web framework, many have fallen victim to common mistakes that reduce code quality, performance, reliability, stability, scalability, and maintainability. Even experienced developers will find that they can reevaluate the work they've done and make it better. In this session, Chad Pytel will provide an overview of some of these common mistakes as well as take questions from the audience and provide real-world advice. Bring your issues and get expert advice on how to bring your code in line with today's best practices.

1. Our Presentation Will Begin Shortly
Rails AntiPatterns
Workshop
May 12, 2011
Matt Reider, Director of Training
Engine Yard
Chad Pytel, Founder & CEO
thoughtbot Inc.

2. Rake Tasks

3. Are you testing them?

4. What makes them hard to test?
• Scripts that live outside app
• Often have network and file access
• Often have output

5. Example Task
namespace :twitter do
task :search => :environment do
puts "Searching twitter."
Twitter.search("@cpytel").each do |result|
puts "Processing #{result.inspect}."
alert = Alert.create(:body => result)
alert.save_cache_file!
end
end
puts "All done!"
end

6. One possible way to test

7. context "rake twitter:search" do
setup do
# How slow is this going to be? Very.
@out = `cd #{Rails.root} &&
rake twitter:search 2>&1`
end

8. should "print a message at the beginning" do
assert_match /Searching/i, @out
end

9. should "find all tweets containing @cpytel" do
# this one would be based entirely on luck.
end

10. This Has Problems
• Slow
• No mocking or stubbing available
• Task isn’t in a transaction

11. Basically, no sandboxing

12. How do we fix this?

13. Rake tasks are just Ruby

14. Move it all into the Model

15. class Alert < ActiveRecord::Base
def self.create_all_from_twitter_search(output = $stdout)
output.puts "Searching twitter."
Twitter.search("@cpytel").each do |result|
output.puts "Processing #{result.inspect}."
alert = create(:body => result)
alert.save_cache_file!
end
output.puts "All done!"
end
def save_cache_file!
# Removes a file from the filesystem.
end
end

16. The Task is Nice and Skinny
namespace :twitter do
task :search => :environment do
Alert.create_all_from_twitter_search
end
end

17. Testing is Pretty Normal
# test/unit/alert_test.rb
class AlertTest < ActiveSupport::TestCase
context "create_all_from_twitter_search" do
setup do
# Make sure none of the tests below hit the
# network or touch the filesystem.
Alert.any_instance.stubs(:save_cache_file!)
Twitter.stubs(:search).returns([])
@output = StringIO.new
end

18. should "print a message at the beginning" do
Alert.create_all_from_twitter_search(@output)
assert_match /Searching/i, @output.string
end

19. should "save some cache files" do
Twitter.stubs(:search).returns(["one"])
alert = mock("alert")
alert.expects(:save_cache_file!)
Alert.stubs(:create).returns(alert)
Alert.create_all_from_twitter_search(@output)
end

20. should "find all tweets containing @cpytel" do
Twitter.expects(:search).
with("@cpytel").
returns(["body"])
Alert.create_all_from_twitter_search(@output)
end

21. We can mock and stub!

22. We can use normal tools!
• FakeWeb/WebMock
• FileUtils::NoWrite

23. In Summary
• You can test drive development of
your rake tasks
• Rake tasks should live inside a
model (or class)

24. Views

25. Know Your Helpers

26. Know How They Change

27. # Edit form
<%= form_for :user,
:url => user_path(@user),
:html => {:method => :put} do |form| %>

28. <%= form_for @user do |form| %>

29. <!-- posts/index.html.erb -->
<% @posts.each do |post| -%>
<h2><%= post.title %></h2>
<%= format_content post.body %>
<p>
<%= link_to 'Email author',
mail_to(post.user.email) %>
</p>
<% end -%>

30. Move the post content
into a partial

31. <!-- posts/index.html.erb -->
<% @posts.each do |post| -%>
<%= render :partial => 'post', :object => :post %>
<% end -%>
<!-- posts/_post.erb -->
<h2><%= post.title %></h2>
<%= format_content post.body %>
<p><%= link_to 'Email author',
mail_to(post.user.email) %></p>

32. Looping was built
into render

33. <!-- posts/index.html.erb -->
<%= render :partial => 'post', :collection => @posts %>
<!-- posts/_post.erb -->
<h2><%= post.title %></h2>
<%= format_content post.body %>
<p>
<%= link_to 'Email author',
mail_to(post.user.email) %>
</p>

34. <!-- posts/index.html.erb -->
<%= render :partial => 'post', :collection => @posts %>
<!-- posts/_post.erb -->
<h2><%= post.title %></h2>
<%= format_content post.body %>
<p>
<%= link_to 'Email author',
mail_to(post.user.email) %>
</p>

35. <%= render :partial => @posts %>

36. <%= render @posts %>

37. Dynamic Page Titles

38. <!-- layouts/application.html.erb -->
<head>
<title>
Acme Widgets : TX-300 Utility Widget
</title>
</head>

39. class PagesController < ApplicationController
def show
@widget = Widgets.find(params[:id])
@title = @widget.name
end
end
<!-- layouts/application.html.erb -->
<head>
<title>Acme Widgets : <%= @title %></title>
</head>

40. This is all View

41. There is a Helper

42. <!-- layouts/application.html.erb -->
<head>
<title>
Acme Widgets : <%= yield(:title) %>
</title>
</head>
<!-- widgets/show.html.erb -->
<% content_for :title, @widget.title %>

43. Default Title

44. <!-- layouts/application.html.erb -->
<head>
<title>
Acme Widgets : <%= yield(:title) || "Home" %>
</title>
</head>

45. What else can we use
this for?

46. <!-- layouts/application.html.erb -->
<div class="sidebar">
This is content for the sidebar.
<%= link_to "Your Account", account_url %>
</div>
<div class="main">
The main content of the page
</div>

47. <!-- layouts/application.html.erb -->
<%= yield(:sidebar) %>
<div class="main">
The main content of the page
</div>
<!-- layouts/application.html.erb -->
<% content_for :sidebar do %>
<div class="sidebar">
This is content for the sidebar.
<%= link_to "Your Account", account_url %>
</div>
<% end %>

48. Avoid Duplication

49. <!-- layouts/application.html.erb -->
<div class="sidebar">
<%= yield(:sidebar) %>
</div>
<div class="main">
The main content of the page
</div>
<!-- layouts/application.html.erb -->
<% content_for :sidebar do %>
This is content for the sidebar.
<%= link_to "Your Account", account_url %>
<% end %>

50. Conditional Sidebar
<!-- layouts/application.html.erb -->
<% if content_for?(:sidebar) -%>
<div class="sidebar">
<%= yield(:sidebar) %>
</div>
<% end -%>
<div class="main">
The main content of the page
</div>
<!-- app/views/products/show.html.erb -->
<% content_for :sidebar do %>
This is content for the sidebar.
<%= link_to "Your Account", account_url %>
<% end %>

51. Upcoming Classes
Zero to Rails 3 in four days
•May 23-26
•Virtual
Rails AntiPatterns
•Best Practices
•Boston – June 6 & 7
•San Francisco – June 13 & 14
Learn more at: Engineyard.com/university