WARNING: You can install the rails gem by typing +gem install rails+, if you don't have it already. Follow the instructions in the "Rails 3 Release Notes":/3_0_release_notes.html
Rails will set you up with what seems like a huge amount of stuff for such a tiny command! You've got the entire Rails directory structure now with all the code you need to run our simple application right out of the box.
The +rails server+ command launches a small web server named WEBrick which comes bundled with Ruby. You'll use this any time you want to access your application through a web browser.
With just three commands we whipped up a Rails server listening on port 3000. Go to your browser and open "http://localhost:3000":http://localhost:3000, you will see a basic Rails app running.
The +rails generate+ command uses templates to create a whole lot of things. You can always find out what's available by running +rails generate+ by itself. Let's do that:
Using generators will save you a large amount of time by writing *boilerplate code*, code that is necessary for the app to work, but not necessary for you to spend time writing. That's what we have computers for.
INFO: All Rails console utilities have help text. As with most *nix utilities, you can try adding +--help+ or +-h+ to the end, for example +rails server --help+.
The controller generator is expecting parameters in the form of +generate controller ControllerName action1 action2+. Let's make a +Greetings+ controller with an action of *hello*, which will say something nice to us.
What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a javascript file and a stylesheet file.
WARNING: Make sure that you do not have any "tilde backup" files in +app/views/(controller)+, or else WEBrick will _not_ show the expected output. This seems to be a *bug* in Rails 2.3.0.
INFO: With a normal, plain-old Rails application, your URLs will generally follow the pattern of http://(host)/(controller)/(action), and a URL like http://(host)/(controller) will hit the *index* action of that controller.
NOTE: For a list of available field types, refer to the "API documentation":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html#method-i-column for the column method for the +TableDefinition+ class.
But instead of generating a model directly (which we'll be doing later), let's set up a scaffold. A *scaffold* in Rails is a full set of model, database migration for that model, controller to manipulate it, views to view and manipulate the data, and a test suite for each of the above.
The generator checks that there exist the directories for models, controllers, helpers, layouts, functional and unit tests, stylesheets, creates the views, controller, model and database migration for HighScore (creating the +high_scores+ table and fields), takes care of the route for the *resource*, and new tests for everything.
The migration requires that we *migrate*, that is, run some Ruby code (living in that +20100209025147_create_high_scores.rb+) to modify the schema of our database. Which database? The sqlite3 database that Rails will create for you when we run the +rake db:migrate+ command. We'll talk more about Rake in-depth in a little while.
INFO: Let's talk about unit tests. Unit tests are code that tests and makes assertions about code. In unit testing, we take a little part of code, say a method of a model, and test its inputs and outputs. Unit tests are your friend. The sooner you make peace with the fact that your quality of life will drastically increase when you unit test your code, the better. Seriously. We'll make one in a moment.
Go to your browser and open "http://localhost:3000/high_scores":http://localhost:3000/high_scores, now we can create new high scores (55,160 on Space Invaders!)
The +console+ command lets you interact with your Rails application from the command line. On the underside, +rails console+ uses IRB, so if you've ever used it, you'll be right at home. This is useful for testing out quick ideas with code and changing data server-side without touching the website.
+rails dbconsole+ figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL, PostgreSQL, SQLite and SQLite3.
Rake is Ruby Make, a standalone Ruby utility that replaces the Unix utility 'make', and uses a 'Rakefile' and +.rake+ files to build up a list of tasks. In Rails, Rake is used for common administration tasks, especially sophisticated ones that build off of each other.
You can get a list of Rake tasks available to you, which will often depend on your current directory, by typing +rake --tasks+. Each task has a description, and should help you find the thing you need.
<shell>
$ rake --tasks
(in /home/foobar/commandsapp)
rake db:abort_if_pending_migrations # Raises an error if there are pending migrations
rake db:charset # Retrieves the charset for the current environment's database
rake db:collation # Retrieves the collation for the current environment's database
rake db:create # Create the database defined in config/database.yml for the current Rails.env
...
...
rake tmp:pids:clear # Clears all files in tmp/pids
rake tmp:sessions:clear # Clears all files in tmp/sessions
rake tmp:sockets:clear # Clears all files in tmp/sockets
</shell>
h4. +about+
<tt>rake about</tt> gives information about version numbers for Ruby, RubyGems, Rails, the Rails subcomponents, your application's folder, the current Rails environment name, your app's database adapter, and schema version. It is useful when you need to ask for help, check if a security patch might affect you, or when you need some stats for an existing Rails installation.
You can precompile the assets in <tt>app/assets</tt> using <tt>rake assets:precompile</tt> and remove compiled assets using <tt>rake assets:clean</tt>.
h4. +db+
The most common tasks of the +db:+ Rake namespace are +migrate+ and +create+, and it will pay off to try out all of the migration rake tasks (+up+, +down+, +redo+, +reset+). +rake db:version+ is useful when troubleshooting, telling you the current version of the database.
If you want to strip out or rebuild any of the Rails documentation (including this guide!), the +doc:+ namespace has the tools. Stripping documentation is mainly useful for slimming your codebase, like if you're writing a Rails application for an embedded platform.
h4. +notes+
These tasks will search through your code for commented lines beginning with "FIXME", "OPTIMIZE", "TODO", or any custom annotation (like XXX) and show you them.
h4. +routes+
+rake routes+ will list all of your defined routes, which is useful for tracking down routing problems in your app, or giving you a good overview of the URLs in an app you're trying to get familiar with.
h4. +test+
INFO: A good description of unit testing in Rails is given in "A Guide to Testing Rails Applications":testing.html
Rails comes with a test suite called Test::Unit. It is through the use of tests that Rails itself is so stable, and the slew of people working on Rails can prove that everything works as it should.
The +test:+ namespace helps in running the different tests you will (hopefully!) write.
h4. +tmp+
The <tt>Rails.root/tmp</tt> directory is, like the *nix /tmp directory, the holding place for temporary files like sessions (if you're using a file store for files), process id files, and cached actions. The +tmp:+ namespace tasks will help you clear them if you need to if they've become overgrown, or create them in case of deletions gone awry.
h4. Miscellaneous
* +rake stats+ is great for looking at statistics on your code, displaying things like KLOCs (thousands of lines of code) and your code to test ratio.
* +rake secret+ will give you a pseudo-random key to use for your session secret.
* <tt>rake time:zones:all</tt> lists all the timezones Rails knows about.
More advanced use of the command line is focused around finding useful (even surprising at times) options in the utilities, and fitting those to your needs and specific work flow. Listed here are some tricks up Rails' sleeve.
When creating a new Rails application, you have the option to specify what kind of database and what kind of source code management system your application is going to use. This will save you a few minutes, and certainly many keystrokes.
Let's see what a +--git+ option and a +--database=postgresql+ option will do for us:
We had to create the *gitapp* directory and initialize an empty git repository before Rails would add files it created to our repository. Let's see what it put in our database configuration:
It also generated some lines in our database.yml configuration corresponding to our choice of PostgreSQL for database.
NOTE. The only catch with using the SCM options is that you have to make your application's directory first, then initialize your SCM, then you can run the +rails new+ command to generate the basis of your app.
Many people have created a large number different web servers in Ruby, and many of them can be used to run Rails. Since version 2.3, Rails uses Rack to serve its webpages, which means that any webserver that implements a Rack handler can be used. This includes WEBrick, Mongrel, Thin, and Phusion Passenger (to name a few!).
NOTE: For more details on the Rack integration, see "Rails on Rack":rails_on_rack.html.
