Rails 3 generators allow for more modularity and customization compared to previous versions. The generators are now built with Thor which maps command line arguments to Ruby classes in a cleaner way. This makes it easier to override defaults and create custom generators. Developers can now build their own generators that integrate with Rails and allow switching components like changing the ORM or template engine.

1. Rails 3 generators
By: Josh Moore

2. About Me
✤ Josh Moore (
✤ www.codingforrent.com
✤ twitter.com/codingforrent
✤ http://github.com/joshsmoore
✤ Ruby
✤ Watir at work
✤ Rails on the Google App Engine for hobby
✤ maintain rails_dm_datastore gem

3. Does anybody mind if I use
English?

4. Contents
✤ Why you need Rails 3 generators
✤ What is new with Rails 3 generators /thor
✤ Creating your own generator
✤ Demo

5. Why should you care?

6. The Problem
Date

7. The Problem
✤ You cannot deviate from the rails convection without losing
productivity.
✤ Who uses something besides the normal rails libraries?
✤ ERB, ActiveRecord, Test::Unit, fixtures
✤ The generators are not nearly as nice as they used to be.

8. Are you sure this is a big deal?
✤ I use DataMapper, Haml
✤ Generator for views does not work
✤ Generator for models does not work
✤ Scaffold does not work

9. Fixing it
✤ Pretty much impossible in Rails 2
✤ You could make your own generator, but not integrated different
names or syntax

10. Rails 3 goal
✤ Modularity - Easy to switch components
✤ But, the generators still produce the same objects by default
✤ ActiveRecord
✤ TestUnit
✤ ERB

11. How does Rails 3 help?
✤ Meta Generators
✤ Scaffold is now a meta generator
✤ Hooks
✤ Internals are complete new - rebuilt with Thor

12. How does that apply to me?
✤ Demo

13. Scaffold Meta Generator
✤ Actually does not generator anything, just hooks into other generators
✤ Scaffold - orm, scaffold-controller
✤ ActiveRecord - test-framework
✤ TestUnit - fixture-replacement
✤ ScaffoldController - template-engine

14. List of hooks
✤ test_framework ✤ orm
✤ webrat ✤ performance_tool
✤ resource_controller ✤ generator
✤ template_engine ✤ scaffold_controller
✤ integration_tool ✤ helper

15. Hooks
✤ Allow one generator to invoke another generator
✤ Can control what generator is invoked
✤ Allow you to override the defaults
✤ Create custom hooks if you want to

16. Override the defaults
✤ For each command
✤ --template-engine=haml
✤ --orm=datamapper
✤ Change the default in config/application.rb
config.generators do |g|
g.orm :datamapper
g.template_engine :haml
g.test_framework :test_unit, :fixture_replacement
=> :factory_girl
end

17. Thor
✤ “Map options to a class. Simply create a class with the appropriate
annotations and have options automatically map to functions and
parameters.”
✤
✤ Plan English: Replacement for Rake and sake with a sane way to pass
parameters, which means it makes it easy to map command line
arguments to parameters and methods in a Ruby class

18. > thor app:install myname --force
> thor app -L
class App < Thor
map "-L" => :list
desc "install APP_NAME", "install one of the available apps"
method_options :force => :boolean, :alias => :string
def install(name)
user_alias = options[:alias]
if options.force?
puts "forcing deletion"
end
puts 'installing'
end
desc "list [SEARCH]", "list all of the available apps, limited by SEARCH"
def list(search="")
# list everything
if search == ""
puts "searching everything"
else
puts "searching for #{search}"
end
end
end

19. Things that are hard in Rake
✤ --force - boolean parameters are harder
✤ mapping -L to the app:list action
✤ parameters mapped to Ruby types (boolean, string, number, array,
and hash)

20. What does this mean for Rails
generators?
✤ Thor::Actions
✤ General purpose actions
✤ Rails::Generators::Actions
✤ actions specific to rails
✤ Application templates and Rails generators now share same API
(Thor::Actions)

21. Building your own generator

22. There’s a generator for that
✤ rails g generator NAME
✤ creates these files
✤ haml/
✤ haml_generator.rb - Gets called when you execute the generator
✤ USAGE - Describes the generator
✤ templates/ - templates go here

23. haml_generator.rb Explained
Code
✤ Place your code in instance methods
✤ It has access to all arguments and options
✤ All public instance methods will be executed (probably in the order
that the methods are defined in)
✤ Inherits from Thor::Group

24. haml_generator.rb Explained
Parameters
✤ Arguments and options
✤ Arguments are non-named parameters that come first
✤ Options are named parameters that come last
✤ Straight from Thor

25. Arguments
✤ Described at the top of your class
✤ The order they are declared is the order they will be accepted on the
command line

26. Arguments Example
class HamlGenerator < Rails::Generators::NamedBase
argument :test_arg, :type => :numeric, :banner => '<number of units>'
argument :test_arg3, :type => :string, :required => false, :default => 'default'

27. Declaring Arguments
✤ :desc - Description for the argument.
✤ :required, :optional - If the argument is required or not.
✤ :type - The type of the argument, can be
✤ :string, :hash, :array, :numeric.
✤ :default - Default value for this argument. It cannot be required and
have default values.
✤ :banner - String that shows the input format

28. Argument Rules
✤ Once an argument is declared optional all remaining arguments must
be optional
✤ you cannot “miss” an optional argument
✤ Once an array argument is declared it will parse everything option
after it into the array
✤ Access the value of the argument by calling its name (attr_accessor)
✤ Required by default

29. Options
✤ Also described at the top of your class
✤ But, the order does not matter

30. Option Example
class HamlGenerator < Rails::Generators::NamedBase
class_option :test_arg, :type => :numeric, :banner => '<number of units>'
class_option :test_arg3, :type => :string, :required => false, :default => 'default'

31. Declaring a class_option
✤ :desc - Description for the argument.
✤ :required, :optional - If the argument is required or not.
✤ :type - The type of the argument, can be
✤ :boolean, :numeric, :hash, :array, :string
✤ :default - Default value for this argument. It cannot be required and
have default values.
✤ :banner - String that shows the input format

32. class_option rules
✤ use the --name-of-class-option to set the class option
✤ optional by default
✤ underscores (_) in option name become dashes (-)

33. Implementing Hooks
✤ simply call hook_for :<NAME>
✤ switches provided --[no|skip]-test-framework
✤ under the hood
✤ creates a class_option
✤ invokes “invoke_from_option”

34. Example

35. Questions?