Ruby on Rails: Plugin Development 101 (...and some...)

Public archival of a presentation I did back in 2009 for a small crowd of university students in Athens, Greece.

Transcript

1. Ruby on Rails: Plug-in Development 101 ...and some... by Jim Myhrberg http://jimeh.me/
2. The Basics Helpers Controller Methods Controllers, Helpers & Views
3. to get you started The Basics
4. Generate a Plug-in $ script/generate plugin hello_world
5. install.rb is executed once during installation. init.rb is the only file included by Rails. The lib folder is your sanctuary. Aside from hello_world.rb, place all Ruby source files in lib/hello_world/ to avoid naming collisions.
6. Example: Collecta_ruby
7. install.rb copies collecta.yml to Rails’ config folder during installation. init.rb requires lib/collecta.rb, loads settings from installed collecta.yml and applies them to the Collecta class. lib/collecta.rb is the ‘heart’ of the plug-in. Single-file Plug-in
8. install.rb require "rubygems" require "fileutils" dir = File.dirname(__FILE__) templates = File.join(dir, "templates") files = [ File.join("config", "collecta.yml") ] files.each do |file| if !File.exist?(File.join(RAILS_ROOT, file)) FileUtils.cp File.join(templates, file), File.join(RAILS_ROOT, file) end end
9. init.rb if defined? Rails require "collecta" config_file = File.join(RAILS_ROOT, "config", "collecta.yml") if File.exist?(config_file) config = YAML.load_file(config_file) if !config[RAILS_ENV.to_s].nil? && !config[RAILS_ENV.to_s]["api_key"].nil? Collecta.api_key = config[RAILS_ENV.to_s]["api_key"] end end end
10. collecta.rb require "rubygems" require "net/http" require "uri" require "cgi" require "json" require "xml" class Collecta @@api_key = nil @@api_url = "http://api.collecta.com/search" # rest of the class... end
11. Example: Facebooker Plus
12. init.rb requires all needed files from lib folder, and calls an init method too boot the plugin. Notice how all files are located under lib/facebooker_plus/. This avoids any naming collisions from other plug-ins, gems, or system. Multi-file Plug-in
13. init.rb if defined? Rails if defined? Facebooker require 'facebooker_plus/facebooker_plus' require 'facebooker_plus/rails/fb_sig_add' require 'facebooker_plus/rails/controller' require 'facebooker_plus/rails/helper' require 'facebooker_plus/extensions/action_controller' require 'facebooker_plus/extensions/action_view' require 'facebooker_plus/extensions/session' FacebookerPlus::Base.init(defined?(config) ? config : nil) else STDERR.puts "** [FacebookerPlus] ERROR: Please load Facebooker before Facebooker Plus.\n" end end
14. create or overload helpers Helpers
15. One of the simplest things to implement in a Plug-in.
16. action_view.rb
17. action_view.rb ActionView::Base.send(:include, FacebookerPlus::Rails::Helper)
18. helper.rb
19. helper.rb module FacebookerPlus module Rails module Helper def url_for(options = {}) options.is_a?(Hash) ? super(options) : fb_sig_add(super(options)) end def form_for(record_or_name_or_array, *args, &proc) args[0][:url] = fb_sig_add(args[0][:url]) if !args[0][:url].nil? super(record_or_name_or_array, *args, &proc) end end end end
20. access custom methods in all controllers Controller Methods
21. Makes it easy to control different aspects of your plug- in from within controllers. Easily create global before/after filters which run from your plug-in. Create class methods to enable/disable your plugin on a per-controller basis.
22. action_controller.rb
23. action_controller.rb module ::ActionController class Base def self.inherited_with_facebooker_plus(subclass) inherited_without_facebooker_plus(subclass) if subclass.to_s == "ApplicationController" subclass.send(:include, FacebookerPlus::Rails::Controller) end end class << self alias_method_chain :inherited, :facebooker_plus end end end
24. controller.rb
25. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods end def send_p3p_headers if !params[:fb_sig_in_iframe].blank? headers['P3P'] = 'CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"' end end def url_for(options = {}) fb_sig_add(super(options)) rescue super(options) end module ClassMethods def init_facebooker_plus(options = {}) before_filter :send_p3p_headers end end end end end
26. Fancy initialization
27. application_controller.rb class ApplicationController < ActionController::Base init_facebooker_plus(:app_class => "App") end
28. application_controller.rb class ApplicationController < ActionController::Base init_facebooker_plus(:app_class => "App") end
29. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods end def set_facebooker_plus_options(options = {}) @facebooker_plus_options = options end def apply_facebooker_options(options = {}) if @facebooker_plus_options.has_key?(:app_class) then end end def create_session_cookie_if_needed # magic happens here end module ClassMethods def init_facebooker_plus(options = {}) before_filter { |controller| controller.set_facebooker_plus_options(options) } before_filter :create_session_cookie_if_needed before_filter :apply_facebooker_options end end end end end
30. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods end def set_facebooker_plus_options(options = {}) @facebooker_plus_options = options end def apply_facebooker_options(options = {}) if @facebooker_plus_options.has_key?(:app_class) then end end def create_session_cookie_if_needed # magic happens here end module ClassMethods def init_facebooker_plus(options = {}) before_filter { |controller| controller.set_facebooker_plus_options(options) } before_filter :create_session_cookie_if_needed before_filter :apply_facebooker_options end end end end end
31. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods end def set_facebooker_plus_options(options = {}) @facebooker_plus_options = options end def apply_facebooker_options(options = {}) if @facebooker_plus_options.has_key?(:app_class) then end end def create_session_cookie_if_needed # magic happens here end module ClassMethods def init_facebooker_plus(options = {}) before_filter { |controller| controller.set_facebooker_plus_options(options) } before_filter :create_session_cookie_if_needed before_filter :apply_facebooker_options end end end end end
32. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods end def set_facebooker_plus_options(options = {}) @facebooker_plus_options = options end def apply_facebooker_options(options = {}) if @facebooker_plus_options.has_key?(:app_class) then end end def create_session_cookie_if_needed # magic happens here end module ClassMethods def init_facebooker_plus(options = {}) before_filter { |controller| controller.set_facebooker_plus_options(options) } before_filter :create_session_cookie_if_needed before_filter :apply_facebooker_options end end end end end
33. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods end def set_facebooker_plus_options(options = {}) @facebooker_plus_options = options end def apply_facebooker_options(options = {}) if @facebooker_plus_options.has_key?(:app_class) then end end def create_session_cookie_if_needed # magic happens here end module ClassMethods def init_facebooker_plus(options = {}) before_filter { |controller| controller.set_facebooker_plus_options(options) } before_filter :create_session_cookie_if_needed before_filter :apply_facebooker_options end end end end end
34. full controllers, helpers and views in your plug-in Controllers, Helpers & Views
35. Very useful in some scenarios when complex functionality is needed. New Relic’s RPM plug-in uses it to display application performance under http://localhost:3000/newrelic. Decently complex to setup.
36. init.rb if defined? Rails if defined? Facebooker require 'facebooker_plus/facebooker_plus' require 'facebooker_plus/rails/fb_sig_add' require 'facebooker_plus/rails/controller' require 'facebooker_plus/rails/helper' require 'facebooker_plus/extensions/action_controller' require 'facebooker_plus/extensions/action_view' require 'facebooker_plus/extensions/session' FacebookerPlus::Base.init(defined?(config) ? config : nil) else STDERR.puts "** [FacebookerPlus] ERROR: Please load Facebooker before Facebooker Plus.\n" end end
37. init.rb if defined? Rails if defined? Facebooker require 'facebooker_plus/facebooker_plus' require 'facebooker_plus/rails/fb_sig_add' require 'facebooker_plus/rails/controller' require 'facebooker_plus/rails/helper' require 'facebooker_plus/extensions/action_controller' require 'facebooker_plus/extensions/action_view' require 'facebooker_plus/extensions/session' FacebookerPlus::Base.init(defined?(config) ? config : nil) else STDERR.puts "** [FacebookerPlus] ERROR: Please load Facebooker before Facebooker Plus.\n" end end
38. facebooker_plus.rb
39. facebooker_plus.rb module FacebookerPlus class Base def self.init(rails_config) controller_path = File.join(facebooker_plus_root, 'lib', 'facebooker_plus', 'rails', 'app', 'controllers') helper_path = File.join(facebooker_plus_root, 'lib', 'facebooker_plus', 'rails', 'app', 'helpers') $LOAD_PATH << controller_path $LOAD_PATH << helper_path if defined? ActiveSupport::Dependencies ActiveSupport::Dependencies.load_paths << controller_path ActiveSupport::Dependencies.load_paths << helper_path elsif defined? Dependencies.load_paths Dependencies.load_paths << controller_path Dependencies.load_paths << helper_path else to_stderr "ERROR: Rails version #{(RAILS_GEM_VERSION) ? RAILS_GEM_VERSION : ''} too old." return end if rails_config rails_config.controller_paths << controller_path else current_paths = ActionController::Routing.controller_paths if current_paths.nil? || current_paths.empty? to_stderr "WARNING: Unable to modify the routes in this version of Rails. Developer mode not available." end current_paths << controller_path end end # more code here end end
40. facebooker_plus.rb controller_path = File.join(facebooker_plus_root, 'lib', 'facebooker_plus', 'rails', 'app', 'controllers') helper_path = File.join(facebooker_plus_root, 'lib', 'facebooker_plus', 'rails', 'app', 'helpers') $LOAD_PATH << controller_path $LOAD_PATH << helper_path
41. facebooker_plus.rb if defined? ActiveSupport::Dependencies ActiveSupport::Dependencies.load_paths << controller_path ActiveSupport::Dependencies.load_paths << helper_path elsif defined? Dependencies.load_paths Dependencies.load_paths << controller_path Dependencies.load_paths << helper_path else to_stderr "ERROR: Rails version #{(RAILS_GEM_VERSION) ? RAILS_GEM_VERSION : ''} too old." return end
42. facebooker_plus.rb if rails_config rails_config.controller_paths << controller_path else current_paths = ActionController::Routing.controller_paths if current_paths.nil? || current_paths.empty? to_stderr "WARNING: Unable to modify the routes in this version of Rails. " + "Developer mode not available." end current_paths << controller_path end
43. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods view_path = File.join(File.dirname(__FILE__), "app", "views") if controller.public_methods.include?("append_view_path") # rails 2.1+ controller.append_view_path(view_path) elsif controller.public_methods.include?("view_paths") # rails 2.0+ controller.view_paths << view_path else # rails <2.0 controller.template_root = view_path end end end end end
44. controller.rb module FacebookerPlus module Rails module Controller def self.included(controller) controller.extend ClassMethods view_path = File.join(File.dirname(__FILE__), "app", "views") if controller.public_methods.include?("append_view_path") # rails 2.1+ controller.append_view_path(view_path) elsif controller.public_methods.include?("view_paths") # rails 2.0+ controller.view_paths << view_path else # rails <2.0 controller.template_root = view_path end end end end end
45. The Plug-in “app” folder
46. Collecta_ruby source: http://github.com/jimeh/collecta_ruby Facebooker Plus source: http://github.com/jimeh/facebooker_plus Railscasts: Making a Plug-in: http://railscasts.com/episodes/33-making-a-plugin email: contact@jimeh.me — twitter: @jimeh slideshare: http://www.slideshare.net/jimeh