Ruby Gem Internals by Examples

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Ashlynn Long
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1 SF Software Design in Ruby Meetup Group Ruby Gem Internals by Examples Ben Zhang, 1/14/2014

2 Types of Ruby Gem Features Global Singleton typhoeus, twitter Single Web Feature (MVC method adding) will_piginate, simple_form Mountable Engine rails_admin, resque Global Observers airbrake, newrelic_rpm Command Line Tool rspec, html2haml

3 Choose a Good Interface will_paginate Post.paginate(:page => params[:page], :per_page => 30) kaminari Post.order(:name).page(params[:page]). per_page(30) class Post < ActiveRecord::Base self.per_page = 10 class Post < ActiveRecord::Base paginates_per 50 <%= %> <%= %>

4 Configuration Options: Outcome Kaminari.configure do config config.default_per_page = 25 config.max_per_page = nil

5 Configuration Options: The How module Kaminari def self.configure(&block) = Kaminari::Configuration.new def class Configuration include ActiveSupport::Configurable config_accessor :default_per_page {} config_accessor :max_per_page {}

6 Gem Initialization I #lib/kaminari.rb require 'kaminari/config' module Kaminari require 'kaminari/helpers/paginator' require... if defined? Rails begin require 'kaminari/railtie' require 'rails' require 'kaminari/engine' rescue LoadError #do nothing #lib/kaminari/railtie.rb module Kaminari class Railtie < ::Rails::Railtie if!defined?(rails) &&!defined?(sinatra) initializer 'kaminari' do _app $stderr.puts no framework detected. Kaminari::Hooks.init

7 Gem Initialization II module Kaminari class Hooks def self.init ActiveSupport.on_load(:active_record) do require 'kaminari/models/active_record_extension' ::ActiveRecord::Base.s :include, Kaminari::ActiveRecordExtension begin; require 'data_mapper'; rescue LoadError; if defined? ::DataMapper require 'kaminari/models/data_mapper_extension' ::DataMapper::Collection.s :include, Kaminari::DataMapperExtension::Collection

8 Add methods to controllers module YourGem class Feature def user_agent(request) ApplicationController.s :include, YourGem::Feature class UsersController < ApplicationController def index user_agent(request)

9 Add methods to models # in your code class Artist include Mongoid::Document field :name, type: String embeds_many :instruments # in your gem module Mongoid class Document def self.embeds_many(association) def self.field(field, options={})

10 Add methods to views #lib/kaminari.rb require 'kaminari/helpers/action_view_extension' #lib/kaminari/helpers/action_view_extension.rb module Kaminari module ActionViewExtension def paginate(scope, options = {}, &block) #lib/kaminari/hooks.rb module Kaminari class Hooks def self.init ActiveSupport.on_load(:action_view) do ::ActionView::Base.s :include, Kaminari::ActionViewExtension

11 Add a rake task #lib/erb2haml.rb require 'erb2haml/railtie' if defined?(rails) #lib/erb2haml/railtie.rb require 'erb2haml' require 'rails' module ERb2Haml class Railtie < Rails::Railtie rake_tasks do load 'erb2haml/railties/erb2haml.rake' #lib/erb2haml/railties/erb2haml.rake require 'find' namespace :haml do desc "Perform bulk conversion of all html. erb files to Haml in views folder" task :replace_erbs do Find.find("app/views/") do path #convert files

12 Gem customization approaches YAML file locale files DSL block before {}, after {}, scriptorator Subclassing devise Method Override(reopen gem class) less preferred

13 Gem customization example class RegistrationsController < Devise::RegistrationsController protected def after_update_path_for(resource) user_path(resource) devise_for :users, :controllers => { :registrations => :registrations }

14 A Good Open Source Contributor follows conventions others established cares about backward compatibility has 100% test coverage of his code knows when to meta-program excels at object oriented design is familiar with various design patterns

15 Recommed Readings

Demystifying Rails Plugin Development

Demystifying Rails Plugin Development Nick Plante :: Voices That Matter Professional Ruby Conference November 18th, 2008 Obligatory Introduction Plugins are generalized, reusable code libraries Ext or