Extracting Plugins And Gems From Rails Apps

Josh Nichols technicalpickles.com

Extracting Plugins and Gems from Rails

application

• The good of plugins

• Reasons for creating your own

• Overview of how to extract

• Tools for extracting

• Case studies

• Distributing

Overview

• Productivity!

• Convention over configuration

• Usually sane defaults

• 80/20 rule

• But, can it get any better?

Ruby and Rails notoriety...

Oh yeah it can.

• 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

But guess what?

You can be clever too!

• 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?

• Model stuff

• View helper stuff

• Controller stuff

What you’d probably want to extract

• 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

• Documentation

• RDoc, README

• Clean up plugin layout

• Test your plugin outside your application

• Pull out of your app

• Gem

Overview of extraction

• 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:

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"

• 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

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

• Rails will automatically load this

• Add your special sauce here

Toolbox: init.rb

• 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

• 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

• 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

• Just a class method

• Include InstanceMethods

• Extend ClassMethods

• Whatever other class stuff you need to do

Toolbox: Macro method

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 }

• Use ActionView::TestCase

• Include the module

• Just call your methods, test the output

• For HTML stuff, assert_dom_equals

Toolbox: Testing view stuff

• Fake enough of the environment to get by

• Create ActiveRecord::Base migration to sqlite in memory db

• Migrate a schema

Tools: Testing model stuff

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

• 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

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

View helpers, always includedhttp://github.com/technicalpickles/content_given

Case Study: content_given

Controller stuff, opt in by including modulehttp://github.com/technicalpickles/safety_valve

Case study: safety_valve

Model stuff, macro methodhttp://github.com/technicalpickles/has_markup

Case study: has_markup

• GitHub

• Free

• Easy to collaborate with others

• script/plugin install git://github.com/technicalpickles/ambitious-sphinx.git

• Also supports generating RubyGems

Distributing

• Create a gemspec for your project

• Enable RubyGems for your repository

• http://hasmygembuiltyet.org/

Distributing: Gems

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{josh@technicalpickles.com} 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

$ sudo gem install technicalpickles-jeweler

• 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

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 = "tsaleh@thoughtbot.com"

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

• 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

Craft the perfect gemhttp://github.com/technicalpickles/jeweler

Jeweler

• Rake tasks for creating and validating gemspec

• Rake tasks for bumping the version

• Will automatically write out updated gemspec

Jeweler

$ 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

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 = "josh@technicalpickles.com" 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

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