Extracting Plugins And Gems From Rails Apps


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Rails Plugins and Ruby Gems are the basic mechanism of sharing functionality between multiple projects. This talk will go over extracting functionality into a plugin, testing it, sharing it, and converting it to a gem.

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Extracting Plugins And Gems From Rails Apps

  1. 1. Extracting Plugins and Gems from Rails application Josh Nichols technicalpickles.com
  2. 2. Overview • The good of plugins • Reasons for creating your own • Overview of how to extract • Tools for extracting • Case studies • Distributing Josh Nichols technicalpickles.com
  3. 3. Ruby and Rails notoriety... • Productivity! • Convention over configuration • Usually sane defaults • 80/20 rule • But, can it get any better? Josh Nichols technicalpickles.com
  4. 4. Oh yeah it can. Josh Nichols technicalpickles.com
  5. 5. Enter the third party • Despite it’s goodness, Rails lacks a lot of functionality you’d find in an webapp • Pagination, Authentication, Etc • Do you really want to have to implement this for every app? • The Internet is full of clever bastards that have figured out good practices for these, and released them as plugins and gems Josh Nichols technicalpickles.com
  6. 6. But guess what? Josh Nichols technicalpickles.com
  7. 7. You can be clever too! Josh Nichols technicalpickles.com
  8. 8. Why make your own plugin? • Lets you clean up your code • Focus on core business concerns, not the other stuff • Re-use within your application • DRY • Re-use between applications • Extract something useful out of one app... • ... and have a headstart on the next Josh Nichols technicalpickles.com
  9. 9. What you’d probably want to extract • Model stuff • View helper stuff • Controller stuff Josh Nichols technicalpickles.com
  10. 10. Overview of extraction • Recognize need/want for extracting • Make sure the functionality you want to extract has good coverage • script/generate plugin to start a plugin • Move code into the plugin • Make your code use the plugin • Make sure tests still pass Josh Nichols technicalpickles.com
  11. 11. Overview of extraction • Documentation • RDoc, README • Clean up plugin layout • Test your plugin outside your application • Pull out of your app • Gem Josh Nichols technicalpickles.com
  12. 12. Your toolbox: • Modules • Group related things • Can’t create instances of them • Can ‘mixin’ to classes • ‘include’ a module into a class to add instance methods • ‘extend’ a module into a class to add class methods Josh Nichols technicalpickles.com
  13. 13. module ClassMethods def count() 3 end end module InstanceMethods def yell(message) puts quot;#{message.upcase}!!!!quot; end end class Person include InstanceMethods extend ClassMethods end Person.count @person = Person.new() @person.yell quot;I don't know what we're yelling aboutquot; Josh Nichols technicalpickles.com
  14. 14. Your toolbox: More modules • In your module’s methods, you have access to everything it was mixed into • There’s a callback for when a module is included • Gives you access to the class that included the module • Use this to include/extend other modules • ... or call class methods Josh Nichols technicalpickles.com
  15. 15. module MyPlugin def self.included(base) base.class_eval do include InstanceMethods extend ClassMethods validates_presence_of :awesome end end module InstanceMethods end module ClassMethods end end Josh Nichols technicalpickles.com
  16. 16. Toolbox: init.rb • Rails will automatically load this • Add your special sauce here Josh Nichols technicalpickles.com
  17. 17. Thinking about how the plugin would be used • Make it always available • Include some modules in init.rb • Include a module • include MyAwesomePlugin • Macro method • acts_as_awesome Josh Nichols technicalpickles.com
  18. 18. Toolbox: Always include • Usually do this in init.rb • For Model: • ActiveRecord::Base.class_eval { include MyPlugin } • For Controller: • ActionController::Base.class_eval { include MyPlugin } • For View: • ActionView::Base.class_eval { include MyPlugin } Josh Nichols technicalpickles.com
  19. 19. Toolbox: Include a module • Tell users to include in their classes class User < ActiveRecord::Base include Clearance::Models::User end class UsersController < ApplicationController include Clearance::Controllers::UsersController end Josh Nichols technicalpickles.com
  20. 20. Toolbox: Macro method • Just a class method • Include InstanceMethods • Extend ClassMethods • Whatever other class stuff you need to do Josh Nichols technicalpickles.com
  21. 21. module AwesomePlugin def self.included(base) base.class_eval do extend MacroMethods end end module MacroMethods def acts_as_awesome() include InstanceMethods extend ClassMethods validates_presence_of :awesome end end module InstanceMethods end module ClassMethods end end ActiveRecord::Base.class_eval { include AwesomePlugin } Josh Nichols technicalpickles.com
  22. 22. Toolbox: Testing view stuff • Use ActionView::TestCase • Include the module • Just call your methods, test the output • For HTML stuff, assert_dom_equals Josh Nichols technicalpickles.com
  23. 23. Tools: Testing model stuff • Fake enough of the environment to get by • Create ActiveRecord::Base migration to sqlite in memory db • Migrate a schema Josh Nichols technicalpickles.com
  24. 24. In test/test_helper.rb require 'rubygems' require 'active_record' RAILS_ROOT = File.dirname(__FILE__) require 'logger' RAILS_DEFAULT_LOGGER = Logger.new(quot;#{RAILS_ROOT}/test.logquot;) require File.dirname(__FILE__) + '/../init' # Load the plugin require File.dirname(__FILE__) + '/post.rb' # Test model config = YAML::load(IO.read(File.dirname(__FILE__) + '/database.yml')) ActiveRecord::Base.logger = Logger.new(File.dirname(__FILE__) + quot;/debug.logquot;) ActiveRecord::Base.establish_connection(config[ENV['DB'] || 'plugin_test']) load(File.dirname(__FILE__) + quot;/schema.rbquot;) if File.exist?(File.dirname(__FILE__) + quot;/ schema.rbquot;) Josh Nichols technicalpickles.com
  25. 25. Toolbox: Other testing • Create a rails app within your plugin test layout • test/rails_root • Update Rakefile to run tests from within the test/ rails_root Josh Nichols technicalpickles.com
  26. 26. Rakefile test_files_pattern = 'test/rails_root/test/{unit,functional,other}/**/*_test.rb' Rake::TestTask.new do |t| t.libs << 'lib' t.pattern = test_files_pattern t.verbose = false end Josh Nichols technicalpickles.com
  27. 27. Case Study: content_given View helpers, always included http://github.com/technicalpickles/content_given Josh Nichols technicalpickles.com
  28. 28. Case study: safety_valve Controller stuff, opt in by including module http://github.com/technicalpickles/safety_valve Josh Nichols technicalpickles.com
  29. 29. Case study: has_markup Model stuff, macro method http://github.com/technicalpickles/has_markup Josh Nichols technicalpickles.com
  30. 30. Distributing • GitHub • Free • Easy to collaborate with others • script/plugin install git://github.com/technicalpickles/ ambitious-sphinx.git • Also supports generating RubyGems Josh Nichols technicalpickles.com
  31. 31. Distributing: Gems • Create a gemspec for your project • Enable RubyGems for your repository • http://hasmygembuiltyet.org/ Josh Nichols technicalpickles.com
  32. 32. Gem::Specification.new do |s| s.name = %q{jeweler} s.version = quot;0.1.1quot; s.required_rubygems_version = Gem::Requirement.new(quot;>= 0quot;) if s.respond_to? :required_rubygems_version= s.authors = [quot;Josh Nicholsquot;, quot;Dan Croakquot;] s.date = %q{2008-10-14} s.description = %q{Simple and opinionated helper for creating Rubygem projects on GitHub} s.email = %q{josh@technicalpickles.com} s.files = [quot;Rakefilequot;, quot;README.markdownquot;, quot;TODOquot;, quot;VERSION.ymlquot;, quot;lib/jewelerquot;, quot;lib/ jeweler/active_support.rbquot;, quot;lib/jeweler/bumping.rbquot;, quot;lib/jeweler/errors.rbquot;, quot;lib/ jeweler/gemspec.rbquot;, quot;lib/jeweler/singleton.rbquot;, quot;lib/jeweler/tasks.rbquot;, quot;lib/jeweler/ versioning.rbquot;, quot;lib/jeweler.rbquot;, quot;test/jeweler_test.rbquot;, quot;test/test_helper.rbquot;] s.homepage = %q{http://github.com/technicalpickles/jeweler} s.require_paths = [quot;libquot;] s.rubygems_version = %q{1.2.0} s.summary = %q{Simple and opinionated helper for creating Rubygem projects on GitHub} end Josh Nichols technicalpickles.com
  33. 33. $ sudo gem install technicalpickles-jeweler Josh Nichols technicalpickles.com
  34. 34. Distributing: Versioning • Update gemspec • Update files • Push to github • Kinda annoying to maintain files • Can maintain it with Rake • Give Gem::Spec Rake’s FileList to generate list of file • Write the spec out Josh Nichols technicalpickles.com
  35. 35. spec = Gem::Specification.new do |s| s.name = quot;shouldaquot; s.version = Thoughtbot::Shoulda::VERSION s.summary = quot;Making tests easy on the fingers and eyesquot; s.homepage = quot;http://thoughtbot.com/projects/shouldaquot; s.rubyforge_project = quot;shouldaquot; s.files = FileList[quot;[A-Z]*quot;, quot;{bin,lib,rails,test}/**/*quot;] s.executables = s.files.grep(/^bin/) { |f| File.basename(f) } s.has_rdoc = true s.extra_rdoc_files = [quot;README.rdocquot;, quot;CONTRIBUTION_GUIDELINES.rdocquot;] s.rdoc_options = [quot;--line-numbersquot;, quot;--inline-sourcequot;, quot;--mainquot;, quot;README.rdocquot;] s.authors = [quot;Tammer Salehquot;] s.email = quot;tsaleh@thoughtbot.comquot; s.add_dependency quot;activesupportquot;, quot;>= 2.0.0quot; end desc quot;Generate a gemspec file for GitHubquot; task :gemspec do File.open(quot;#{spec.name}.gemspecquot;, 'w') do |f| f.write spec.to_ruby end end Josh Nichols technicalpickles.com
  36. 36. Distributing: Versioning • Update Rakefile’s Gem::Specification’s version • Run ‘rake gemspec’ • Commit and push • Easy to forget to keep Rakefile and gemspec in sync • Can it get easier? Josh Nichols technicalpickles.com
  37. 37. Jeweler Craft the perfect gem http://github.com/technicalpickles/jeweler Josh Nichols technicalpickles.com
  38. 38. Jeweler • Rake tasks for creating and validating gemspec • Rake tasks for bumping the version • Will automatically write out updated gemspec Josh Nichols technicalpickles.com
  39. 39. $ rake version (in /Users/nichoj/Projects/jeweler) Current version: 0.1.1 $ rake gemspec (in /Users/nichoj/Projects/jeweler) Generated: jeweler.gemspec jeweler.gemspec is valid. $ rake version:bump:minor (in /Users/nichoj/Projects/jeweler) Current version: 0.1.1 Wrote to VERSION.yml: 0.2.0 Generated: jeweler.gemspec $ rake version:bump:patch (in /Users/nichoj/Projects/jeweler) Current version: 0.2.0 Wrote to VERSION.yml: 0.2.1 Generated: jeweler.gemspec $ rake version:bump:major (in /Users/nichoj/Projects/jeweler) Current version: 0.2.1 Wrote to VERSION.yml: 1.0.0 Generated: jeweler.gemspec Josh Nichols technicalpickles.com
  40. 40. Rakefile begin require 'rubygems' require 'jeweler' gemspec = Gem::Specification.new do |s| s.name = quot;has_markupquot; s.summary = quot;Manage markup close to home... right in the model! Caching, validation, etcquot; s.email = quot;josh@technicalpickles.comquot; s.homepage = quot;http://github.com/technicalpickles/has_markupquot; s.description = quot;Manage markup close to home... right in the model! Caching, validation, etcquot; s.authors = [quot;Josh Nicholsquot;] s.files = FileList[quot;[A-Z]*.*quot;, quot;{generators,lib,test,spec}/**/*quot;] end Jeweler.craft(gemspec) rescue LoadError puts quot;Jeweler not available. Install it with: sudo gem install technicalpickles-jeweler -s http://gems.github.comquot; end Josh Nichols technicalpickles.com