Cannot generate a Pages controller in the Rails 3 tutorial - ruby-on-rails

Question

I am working through the Michael Hartl Rails 3 tutorial, and I am currently on Chapter 3. The tutorial asks me to generate a Pages controller with actions for a Home page and a Contact page using the command line: "$ rails generate controller Pages home contact".
This is the output I get:
ruby 1.9.2p290 (2011-07-09) [i386-mingw32]
C:\Users\abcd\rails_projects2\sample_app>rails generate controller Pages home
contact
C:/Users/abcd/rails_projects2/sample_app/config/application.rb:8:in `require':
no such file to load -- sprockets/railtie (LoadError)
from C:/Users/abcd/rails_projects2/sample_app/config/application.rb:8:
in `<top (required)>'
from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/comman
ds.rb:15:in `require'
from C:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.9/lib/rails/comman
ds.rb:15:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
The contents of my config/application.rb file:
require File.expand_path('../boot', __FILE__)
# Pick the frameworks you want:
require "active_record/railtie"
require "action_controller/railtie"
require "action_mailer/railtie"
require "active_resource/railtie"
require "sprockets/railtie"
# require "rails/test_unit/railtie"
if defined?(Bundler)
# If you precompile assets before deploying to production, use this line
Bundler.require *Rails.groups(:assets => %w(development test))
# If you want your assets lazily compiled in production, use this line
# Bundler.require(:default, :assets, Rails.env)
end
module SampleApp
class Application < Rails::Application
# Settings in config/environments/* take precedence over those specified here.
# Application configuration should go into files in config/initializers
# -- all .rb files in that directory are automatically loaded.
# Custom directories with classes and modules you want to be autoloadable.
# config.autoload_paths += %W(#{config.root}/extras)
# Only load the plugins named here, in the order given (default is alphabetical).
# :all can be used as a placeholder for all plugins not explicitly named.
# config.plugins = [ :exception_notification, :ssl_requirement, :all ]
# Activate observers that should always be running.
# config.active_record.observers = :cacher, :garbage_collector, :forum_observer
# Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
# Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
# config.time_zone = 'Central Time (US & Canada)'
# The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
# config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
# config.i18n.default_locale = :de
# Configure the default encoding used in templates for Ruby 1.9.
config.encoding = "utf-8"
# Configure sensitive parameters which will be filtered from the log file.
config.filter_parameters += [:password]
# Enable the asset pipeline
config.assets.enabled = true
# Version of your assets, change this if you want to expire all your assets
config.assets.version = '1.0'
end
end
I have also discovered that when I try to run the command line "rails server", I get a similar error message. I don't know if this information is useful.
Thank you!

Answer 1

It looks like the tutorial is using Rails 3.0.9, but you've created your application using a later version of the Rails gem.
sprockets was added in version 3.1. Even though you've updated your Gemfile to specify Rails 3.0.9, the code that was generated when you ran rails new sample_app is expecting Rails 3.1 gems to be available (i.e. simply changing the Gemfile isn't enough to change the Rails version of the application).
You could try simply commenting out the reference to sprockets in your application.rb file, but even if that works for now it's likely there'll be other differences that'll cause errors later.
Your best bet is probably to start from scratch, but make sure you're using Rails 3.0.9. If you're using RVM, you could create a new gemset and install 3.0.9 into it, then use that gemset.
Alternatively, when you create the application specify the version of the gem you want in the command:
rails _3.0.9_ new sample_app
If you use this second method, then after you've created the application, simply using rails by itself to issue commands (like generate) should be okay, as Rails does some magic to determine the version of the app and use the right gem version, even if a later version is installed - you don't need to use rails _3.0.9_ all the time.

Answer 2

in your config/application.rb file, try to uncomment the "sprockets" line like this:
# require "sprockets/railtie"
Then check if it works afterwards... that should do the trick...
But if not, please check your Gemfile, it should look something like this:
# gem "rails", "~> 3.1.0" # or "3.0.9"
gem "rails" , "3.0.9"
gem 'sqlite3', '1.3.3' # or whatever DB you use
If that still doesn't help, check which version of sprockets you have installed:
in a shell, do a:
$ gem list | grep sprock
sprockets (2.0.0.beta.10)