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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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Josh Nichols technicalpickles.com
Extracting Plugins and Gems from Rails
application
Josh Nichols technicalpickles.com
• The good of plugins
• Reasons for creating your own
• Overview of how to extract
• Tools for extracting
• Case studies
• Distributing
Overview
Josh Nichols technicalpickles.com
• Productivity!
• Convention over configuration
• Usually sane defaults
• 80/20 rule
• But, can it get any better?
Ruby and Rails notoriety...
Josh Nichols technicalpickles.com
Oh yeah it can.
Josh Nichols technicalpickles.com
• 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
Enter the third party
Josh Nichols technicalpickles.com
But guess what?
Josh Nichols technicalpickles.com
You can be clever too!
Josh Nichols technicalpickles.com
• 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
Why make your own plugin?
Josh Nichols technicalpickles.com
• Model stuff
• View helper stuff
• Controller stuff
What you’d probably want to extract
Josh Nichols technicalpickles.com
• 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
Overview of extraction
Josh Nichols technicalpickles.com
• Documentation
• RDoc, README
• Clean up plugin layout
• Test your plugin outside your application
• Pull out of your app
• Gem
Overview of extraction
Josh Nichols technicalpickles.com
• 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
Your toolbox:
Josh Nichols technicalpickles.com
module ClassMethods def count() 3 endend
module InstanceMethods def yell(message) puts "#{message.upcase}!!!!" endend
class Person include InstanceMethods extend ClassMethodsend
Person.count@person = Person.new()@person.yell "I don't know what we're yelling about"
Josh Nichols technicalpickles.com
• 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
Your toolbox: More modules
Josh Nichols technicalpickles.com
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 endend
Josh Nichols technicalpickles.com
• Rails will automatically load this
• Add your special sauce here
Toolbox: init.rb
Josh Nichols technicalpickles.com
• Make it always available
• Include some modules in init.rb
• Include a module
• include MyAwesomePlugin
• Macro method
• acts_as_awesome
Thinking about how the plugin would be used
Josh Nichols technicalpickles.com
• 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 }
Toolbox: Always include
Josh Nichols technicalpickles.com
• Tell users to include in their classes
Toolbox: Include a module
class User < ActiveRecord::Base include Clearance::Models::Userend
class UsersController < ApplicationController include Clearance::Controllers::UsersControllerend
Josh Nichols technicalpickles.com
• Just a class method
• Include InstanceMethods
• Extend ClassMethods
• Whatever other class stuff you need to do
Toolbox: Macro method
Josh Nichols technicalpickles.com
module AwesomePlugindef self.included(base)
base.class_eval doextend MacroMethods
endend
module MacroMethodsdef acts_as_awesome()
include InstanceMethodsextend ClassMethodsvalidates_presence_of :awesome
endend
module InstanceMethodsendmodule ClassMethodsend
endActiveRecord::Base.class_eval { include AwesomePlugin }
Josh Nichols technicalpickles.com
• Use ActionView::TestCase
• Include the module
• Just call your methods, test the output
• For HTML stuff, assert_dom_equals
Toolbox: Testing view stuff
Josh Nichols technicalpickles.com
• Fake enough of the environment to get by
• Create ActiveRecord::Base migration to sqlite in memory db
• Migrate a schema
Tools: Testing model stuff
Josh Nichols technicalpickles.com
require 'rubygems'require 'active_record'
RAILS_ROOT = File.dirname(__FILE__)require 'logger'RAILS_DEFAULT_LOGGER = Logger.new("#{RAILS_ROOT}/test.log")
require File.dirname(__FILE__) + '/../init' # Load the pluginrequire 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__) + "/debug.log")ActiveRecord::Base.establish_connection(config[ENV['DB'] || 'plugin_test'])
load(File.dirname(__FILE__) + "/schema.rb") if File.exist?(File.dirname(__FILE__) + "/schema.rb")
In test/test_helper.rb
Josh Nichols technicalpickles.com
• Create a rails app within your plugin test layout
• test/rails_root
• Update Rakefile to run tests from within the test/rails_root
Toolbox: Other testing
Josh Nichols technicalpickles.com
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 = falseend
Rakefile
Josh Nichols technicalpickles.com
View helpers, always includedhttp://github.com/technicalpickles/content_given
Case Study: content_given
Josh Nichols technicalpickles.com
Controller stuff, opt in by including modulehttp://github.com/technicalpickles/safety_valve
Case study: safety_valve
Josh Nichols technicalpickles.com
Model stuff, macro methodhttp://github.com/technicalpickles/has_markup
Case study: has_markup
Josh Nichols technicalpickles.com
• GitHub
• Free
• Easy to collaborate with others
• script/plugin install git://github.com/technicalpickles/ambitious-sphinx.git
• Also supports generating RubyGems
Distributing
Josh Nichols technicalpickles.com
• Create a gemspec for your project
• Enable RubyGems for your repository
• http://hasmygembuiltyet.org/
Distributing: Gems
Josh Nichols technicalpickles.com
Gem::Specification.new do |s| s.name = %q{jeweler} s.version = "0.1.1"
s.required_rubygems_version = Gem::Requirement.new(">= 0") if s.respond_to? :required_rubygems_version= s.authors = ["Josh Nichols", "Dan Croak"] s.date = %q{2008-10-14} s.description = %q{Simple and opinionated helper for creating Rubygem projects on GitHub} s.email = %q{[email protected]} s.files = ["Rakefile", "README.markdown", "TODO", "VERSION.yml", "lib/jeweler", "lib/jeweler/active_support.rb", "lib/jeweler/bumping.rb", "lib/jeweler/errors.rb", "lib/jeweler/gemspec.rb", "lib/jeweler/singleton.rb", "lib/jeweler/tasks.rb", "lib/jeweler/versioning.rb", "lib/jeweler.rb", "test/jeweler_test.rb", "test/test_helper.rb"] s.homepage = %q{http://github.com/technicalpickles/jeweler} s.require_paths = ["lib"] 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
$ sudo gem install technicalpickles-jeweler
Josh Nichols technicalpickles.com
• 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
Distributing: Versioning
Josh Nichols technicalpickles.com
spec = Gem::Specification.new do |s| s.name = "shoulda" s.version = Thoughtbot::Shoulda::VERSION s.summary = "Making tests easy on the fingers and eyes" s.homepage = "http://thoughtbot.com/projects/shoulda" s.rubyforge_project = "shoulda"
s.files = FileList["[A-Z]*", "{bin,lib,rails,test}/**/*"] s.executables = s.files.grep(/^bin/) { |f| File.basename(f) }
s.has_rdoc = true s.extra_rdoc_files = ["README.rdoc", "CONTRIBUTION_GUIDELINES.rdoc"] s.rdoc_options = ["--line-numbers", "--inline-source", "--main", "README.rdoc"]
s.authors = ["Tammer Saleh"] s.email = "[email protected]"
s.add_dependency "activesupport", ">= 2.0.0"end
desc "Generate a gemspec file for GitHub"task :gemspec do File.open("#{spec.name}.gemspec", 'w') do |f| f.write spec.to_ruby endend
Josh Nichols technicalpickles.com
• 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?
Distributing: Versioning
Josh Nichols technicalpickles.com
Craft the perfect gemhttp://github.com/technicalpickles/jeweler
Jeweler
Josh Nichols technicalpickles.com
• Rake tasks for creating and validating gemspec
• Rake tasks for bumping the version
• Will automatically write out updated gemspec
Jeweler
Josh Nichols technicalpickles.com
$ rake version(in /Users/nichoj/Projects/jeweler)Current version: 0.1.1
$ rake gemspec(in /Users/nichoj/Projects/jeweler)Generated: jeweler.gemspecjeweler.gemspec is valid.
$ rake version:bump:minor(in /Users/nichoj/Projects/jeweler)Current version: 0.1.1Wrote to VERSION.yml: 0.2.0Generated: jeweler.gemspec
$ rake version:bump:patch(in /Users/nichoj/Projects/jeweler)Current version: 0.2.0Wrote to VERSION.yml: 0.2.1Generated: jeweler.gemspec
$ rake version:bump:major(in /Users/nichoj/Projects/jeweler)Current version: 0.2.1Wrote to VERSION.yml: 1.0.0Generated: jeweler.gemspec
Josh Nichols technicalpickles.com
begin require 'rubygems' require 'jeweler' gemspec = Gem::Specification.new do |s| s.name = "has_markup" s.summary = "Manage markup close to home... right in the model! Caching, validation, etc" s.email = "[email protected]" s.homepage = "http://github.com/technicalpickles/has_markup" s.description = "Manage markup close to home... right in the model! Caching, validation, etc" s.authors = ["Josh Nichols"] s.files = FileList["[A-Z]*.*", "{generators,lib,test,spec}/**/*"] end Jeweler.craft(gemspec)rescue LoadError puts "Jeweler not available. Install it with: sudo gem install technicalpickles-jeweler -s http://gems.github.com"end
Rakefile