Rails Antipatterns | Open Session with Chad Pytel

Our Presentation Will Begin Shortly

Rails AntiPatterns
Workshop
May 12, 2011

Matt Reider, Director of Training
Engine Yard

Chad Pytel, Founder & CEO
thoughtbot Inc.

What makes them hard to test?

• Scripts that live outside app
• Often have network and ﬁle access
• Often have output

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

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

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

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

This Has Problems

• Slow
• No mocking or stubbing available
• Task isn’t in a transaction

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

The Task is Nice and Skinny

namespace :twitter do
task :search => :environment do
Alert.create_all_from_twitter_search
end
end

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

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

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

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

We can use normal tools!

• FakeWeb/WebMock
• FileUtils::NoWrite

In Summary

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

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

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

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

Move the post content
into a partial

<% @posts.each do |post| -%>
<%= render :partial => 'post', :object => :post %>
<% end -%>


<p><%= link_to 'Email author',
mail_to(post.user.email) %></p>

Looping was built
into render

<%= render :partial => 'post', :collection => @posts %>


<p>
<%= link_to 'Email author',
mail_to(post.user.email) %>
</p>

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

<head>
<title>
Acme Widgets : TX-300 Utility Widget
</title>
</head>

class PagesController < ApplicationController
def show
@widget = Widgets.find(params[:id])
@title = @widget.name
end
end

<head>
<title>Acme Widgets : <%= @title %></title>
</head>

<head>
<title>
Acme Widgets : <%= yield(:title) %>
</title>
</head>


<% content_for :title, @widget.title %>

<head>
<title>
Acme Widgets : <%= yield(:title) || "Home" %>
</title>
</head>

What else can we use
this for?

<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>

<%= yield(:sidebar) %>

<div class="main">
</div>

<% content_for :sidebar do %>
</div>
<% end %>

</div>

<div class="main">
</div>

<% end %>

Conditional Sidebar
<% if content_for?(:sidebar) -%>
</div>
<% end -%>

<div class="main">
</div>


<% end %>

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

Rails Antipatterns | Open Session with Chad Pytel

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