README

== RottenPotatoes for "Engineering Software for Cloud Computing"

This repo tracks the version of the RottenPotatoes teaching app used
with the Fox & Patterson textbook "Engineering Software for Cloud
Computing".

Different branches of the repo correspond to the code developed in
different chapters of the book.

See the book for information on how to use this repo and what the
branches are for.

== Welcome to Rails

Rails is a web-application framework that includes everything needed to create
database-backed web applications according to the Model-View-Control pattern.

This pattern splits the view (also called the presentation) into "dumb"
templates that are primarily responsible for inserting pre-built data in between
HTML tags. The model contains the "smart" domain objects (such as Account,
Product, Person, Post) that holds all the business logic and knows how to
persist themselves to a database. The controller handles the incoming requests
(such as Save New Account, Update Product, Show Post) by manipulating the model
and directing data to the view.

In Rails, the model is handled by what's called an object-relational mapping
layer entitled Active Record. This layer allows you to present the data from
database rows as objects and embellish these data objects with business logic
methods. You can read more about Active Record in
link:files/vendor/rails/activerecord/README.html.

The controller and view are handled by the Action Pack, which handles both
layers by its two parts: Action View and Action Controller. These two layers
are bundled in a single package due to their heavy interdependence. This is
unlike the relationship between the Active Record and Action Pack that is much
more separate. Each of these packages can be used independently outside of
Rails. You can read more about Action Pack in
link:files/vendor/rails/actionpack/README.html.


== Getting Started

NOTE: The steps below are for creating a new app.  The initial version
of RottenPotatoes was created with Rails 3.0.5 and Ruby 1.8.7 using the
commands:

* <tt>rails new rottenpotatoes -J -T</tt> (creates a new app without
including JavaScript templates and without creating directories for
Test::Unit, since we use RSpec instead)
* <tt>cd rottenpotatoes</tt>
* <tt>rails generate resource movie title:string rating:string
description:text released_on:datetime</tt> (generates a skeleton model,
RESTful controller, RESTful views, test skeletons, and a database
migration for a RESTful resource called 'movie')
* <tt>rake db:migrate</tt> (runs the migration to setup the Movies table)
* <tt>rails generate cucumber:install</tt> (generates files and
directories needed by Cucumber)
* <tt>rails generate rspec:install</tt>  (generates files and
directories needed by RSpec)
* <tt>rm public/index.html</tt>  (removes the default static homepage installed
by Rails)

and then filling in the basic code for the Movie model, views and controller.

1. At the command prompt, create a new Rails application:
       <tt>rails new myapp</tt> (where <tt>myapp</tt> is the application name)

2. Change directory to <tt>myapp</tt> and start the web server:
       <tt>cd myapp; rails server</tt> (run with --help for options)

3. Go to http://localhost:3000/ and you'll see:
       "Welcome aboard: You're riding Ruby on Rails!"

4. Follow the guidelines to start developing your application. You can find
the following resources handy:

* The Getting Started Guide: http://guides.rubyonrails.org/getting_started.html
* Ruby on Rails Tutorial Book: http://www.railstutorial.org/



== Getting Started

1. At the command prompt, create a new Rails application:
       <tt>rails new myapp</tt> (where <tt>myapp</tt> is the application name)

2. Change directory to <tt>myapp</tt> and start the web server:
       <tt>cd myapp; rails server</tt> (run with --help for options)

3. Go to http://localhost:3000/ and you'll see:
       "Welcome aboard: You're riding Ruby on Rails!"

4. Follow the guidelines to start developing your application. You can find
the following resources handy:

* The Getting Started Guide: http://guides.rubyonrails.org/getting_started.html
* Ruby on Rails Tutorial Book: http://www.railstutorial.org/


== Debugging Rails

Sometimes your application goes wrong. Fortunately there are a lot of tools that
will help you debug it and get it back on the rails.

First area to check is the application log files. Have "tail -f" commands
running on the server.log and development.log. Rails will automatically display
debugging and runtime information to these files. Debugging info will also be
shown in the browser on requests from 127.0.0.1.

You can also log your own messages directly into the log file from your code
using the Ruby logger class from inside your controllers. Example:

  class WeblogController < ActionController::Base
    def destroy
      @weblog = Weblog.find(params[:id])
      @weblog.destroy
      logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
    end
  end

The result will be a message in your log file along the lines of:

  Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1!

More information on how to use the logger is at http://www.ruby-doc.org/core/

Also, Ruby documentation can be found at http://www.ruby-lang.org/. There are
several books available online as well:

* Programming Ruby: http://www.ruby-doc.org/docs/ProgrammingRuby/ (Pickaxe)
* Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)

These two books will bring you up to speed on the Ruby language and also on
programming in general.


== Debugger

Debugger support is available through the debugger command when you start your
Mongrel or WEBrick server with --debugger. This means that you can break out of
execution at any point in the code, investigate and change the model, and then,
resume execution! You need to install ruby-debug to run the server in debugging
mode. With gems, use <tt>sudo gem install ruby-debug</tt>. Example:

  class WeblogController < ActionController::Base
    def index
      @posts = Post.find(:all)
      debugger
    end
  end

So the controller will accept the action, run the first line, then present you
with a IRB prompt in the server window. Here you can do things like:

  >> @posts.inspect
  => "[#<Post:0x14a6be8
          @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>,
       #<Post:0x14a6620
          @attributes={"title"=>"Rails", "body"=>"Only ten..", "id"=>"2"}>]"
  >> @posts.first.title = "hello from a debugger"
  => "hello from a debugger"

...and even better, you can examine how your runtime objects actually work:

  >> f = @posts.first
  => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
  >> f.
  Display all 152 possibilities? (y or n)

Finally, when you're ready to resume execution, you can enter "cont".


== Console

The console is a Ruby shell, which allows you to interact with your
application's domain model. Here you'll have all parts of the application
configured, just like it is when the application is running. You can inspect
domain models, change values, and save to the database. Starting the script
without arguments will launch it in the development environment.

To start the console, run <tt>rails console</tt> from the application
directory.

Options:

* Passing the <tt>-s, --sandbox</tt> argument will rollback any modifications
  made to the database.
* Passing an environment name as an argument will load the corresponding
  environment. Example: <tt>rails console production</tt>.

To reload your controllers and models after launching the console run
<tt>reload!</tt>

More information about irb can be found at:
link:http://www.rubycentral.com/pickaxe/irb.html


== dbconsole

You can go to the command line of your database directly through <tt>rails
dbconsole</tt>. You would be connected to the database with the credentials
defined in database.yml. Starting the script without arguments will connect you
to the development database. Passing an argument will connect you to a different
database, like <tt>rails dbconsole production</tt>. Currently works for MySQL,
PostgreSQL and SQLite 3.

== Description of Contents

The default directory structure of a generated Ruby on Rails application:

  |-- app
  |   |-- controllers
  |   |-- helpers
  |   |-- mailers
  |   |-- models
  |   `-- views
  |       `-- layouts
  |-- config
  |   |-- environments
  |   |-- initializers
  |   `-- locales
  |-- db
  |-- doc
  |-- lib
  |   `-- tasks
  |-- log
  |-- public
  |   |-- images
  |   |-- javascripts
  |   `-- stylesheets
  |-- script
  |-- test
  |   |-- fixtures
  |   |-- functional
  |   |-- integration
  |   |-- performance
  |   `-- unit
  |-- tmp
  |   |-- cache
  |   |-- pids
  |   |-- sessions
  |   `-- sockets
  `-- vendor
      `-- plugins

app
  Holds all the code that's specific to this particular application.

app/controllers
  Holds controllers that should be named like weblogs_controller.rb for
  automated URL mapping. All controllers should descend from
  ApplicationController which itself descends from ActionController::Base.

app/models
  Holds models that should be named like post.rb. Models descend from
  ActiveRecord::Base by default.

app/views
  Holds the template files for the view that should be named like
  weblogs/index.html.erb for the WeblogsController#index action. All views use
  eRuby syntax by default.

app/views/layouts
  Holds the template files for layouts to be used with views. This models the
  common header/footer method of wrapping views. In your views, define a layout
  using the <tt>layout :default</tt> and create a file named default.html.erb.
  Inside default.html.erb, call <% yield %> to render the view using this
  layout.

app/helpers
  Holds view helpers that should be named like weblogs_helper.rb. These are
  generated for you automatically when using generators for controllers.
  Helpers can be used to wrap functionality for your views into methods.

config
  Configuration files for the Rails environment, the routing map, the database,
  and other dependencies.

db
  Contains the database schema in schema.rb. db/migrate contains all the
  sequence of Migrations for your schema.

doc
  This directory is where your application documentation will be stored when
  generated using <tt>rake doc:app</tt>

lib
  Application specific libraries. Basically, any kind of custom code that
  doesn't belong under controllers, models, or helpers. This directory is in
  the load path.

public
  The directory available for the web server. Contains subdirectories for
  images, stylesheets, and javascripts. Also contains the dispatchers and the
  default HTML files. This should be set as the DOCUMENT_ROOT of your web
  server.

script
  Helper scripts for automation and generation.

test
  Unit and functional tests along with fixtures. When using the rails generate
  command, template test files will be generated for you and placed in this
  directory.

vendor
  External libraries that the application depends on. Also includes the plugins
  subdirectory. If the app has frozen rails, those gems also go here, under
  vendor/rails/. This directory is in the load path.