Rails Engines. Doing It Wrong. And Then Right.

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1. Rails Engines. Doing it wrong. And then right.
3. @mrreynolds
4. Why Engines? Extend your app with reusable models, controllers, views, helpers, routes, locales and tasks.
5. It‘s an app within an app.
6. Rails::Engine < Rails::Railtie
7. What‘s a Railtie? • Core of the framework • Provides hooks to extend Rails • ActiveRecord, ActionController etc. are all Railties
8. What is an Engine then ?
9. It‘s just a Railtie with some defaults.
10. Typical cases • CMS • Admin Frontend • Translation Frontend
11. Our problem • Build a vocabulary and thesauraus management system • Adjust and extend it for every customer without forking it
12. github.com/innoq/iqvoc
13. First approach • iQvoc as main app • Vendor logic as engine
14. The problem • Could not act as a standalone app • Always had to be plugged into a main app
15. Second approach • Vendor logic as main app • iQvoc as engine (and app)
16. The problem • A Rails 3.0 Engine can not act as a standalone app by default (requires customization) • No out-of-the-box support for migrations, assets etc.
17. Options
18. Wait for Rails 3.1
19. Just hack it.
20. What do you need ?
21. Act as an engine… # lib/engine.rb module Iqvoc class Engine < Rails::Engine end end
22. …only if we want to # config/initializers/iqvoc.rb unless Iqvoc.const_defined?(:Application) require File.join(File.dirname(__FILE__), '../../lib/engine') end # config/application.rb module Iqvoc class Application < Rails::Application
23. Up next: Engine tasks # lib/engine.rb class Engine < Rails::Engine paths.lib.tasks << "lib/engine_tasks" Only available when app is mounted as an engine!
24. What about Migrations? namespace :iqvoc do namespace :db do task :migrate => :environment do ActiveRecord::Migration.verbose = ENV["VERBOSE"] ? ENV["VERBOSE"] == "true" : true path = Iqvoc::Engine.find_root_with_flag("db").join('db/migrate') ActiveRecord::Migrator.migrate(path, ENV["VERSION"] ? ENV["VERSION"].to_i : nil) Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby end end end
26. Rails 3.1 rake railties:copy_migrations
27. Routes Foo.application.routes.draw do Rails.application.routes.draw do
28. Rails 3.1 # Main app Rails.application.routes.draw do mount Foo::Engine => "/foo" end # Engine Foo::Engine.routes.draw do …
29. Rails 3.1 Namespace isolation module MyEngine class Foo < Rails::Engine isolate_namespace Foo end end # Separate routers for each Engine foo.root_path main_app.root_path
30. If you isolate, don‘t forget to move things.
31. app/controllers/foo/things_controller.rb app/views/foo/things/new.html.erb …
32. Assets task :link do Iqvoc.for_static_folders do |source_common_dir, target_common_dir| File.unlink(target_common_dir) if File.symlink?(target_common_dir) && ENV['force'] == "true" if !File.exists?(target_common_dir) puts "Linking #{source_common_dir} -> #{target_common_dir}" File.symlink(source_common_dir, target_common_dir) else puts "Symlink #{target_common_dir} already exists!" end end end
33. Rails 3.1 # ActionDispath::Static config.serve_static_assets = true or rake railties:create_symlinks
34. bundle in hell • No support for multiple locations of a single gem
35. Forget about that: group :development do gem 'iqvoc', :path => '../iqvoc' end group :production do gem 'iqvoc', :git => 'git@github.com:innoq/iqvoc.git' end
36. Forget about that as well:
38. Instead: Separate your Gemfiles
39. Rails 3.0 Engines Rails 3.1 Engines Rails 2.3 Engines
40. Engines = Mountable Apps
42. @drogus Piotr Sarnacki Say thanks to:
43. Thanks!