Guides.rubyonrails.org

Chapters

1. Command Line Basics
   • rails
   • server
   • generate
   • console
   • dbconsole
   • plugin
   • runner
   • destroy
   • about
2. The Rails Advanced Command Line
   • Rails with Databases and SCM
   • server with Different Backends
   • The Rails Generation: Generators
   • Rake is Ruby Make
3. Changelog

1 Command Line Basics

There are a few commands that are absolutely critical to your everyday usage of Rails. In the order of how much you’ll probably use them are:

• console
• server
• rake
• generate
• rails

Let’s create a simple Rails application to step through each of these commands in context.

1.1 rails

The first thing we’ll want to do is create a new Rails application by running the rails command after installing Rails.

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.

1.2 server

Let’s try it! The server command launches a small web server named WEBrick which comes bundled with Ruby. You’ll use this any time you want to view your work through a web browser.

Without any prodding of any kind, server will run our new shiny Rails app:

WHOA. With just three commands we whipped up a Rails server listening on port 3000. Go! Go right now to your browser and go to http://localhost:3000. I’ll wait.

See? Cool! It doesn’t do much yet, but we’ll change that.

1.3 generate

The generate command uses templates to create a whole lot of things. You can always find out what’s available by running generate by itself. Let’s do that:

Using generators will save you a large amount of time by writing boilerplate code for you — necessary for the darn thing to work, but not necessary for you to spend time writing. That’s what we have computers for, right?

Let’s make our own controller with the controller generator. But what command should we use? Let’s ask the generator:

Ah, 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.

Look there! Now what all did this generate? It looks like it made sure a bunch of directories were in our application, and created a controller file, a functional test file, a helper for the view, and a view file.

Let’s check out the controller and modify it a little (in app/controllers/greetings_controller.rb):

Then the view, to display our nice message (in app/views/greetings/hello.html.erb):

Deal. Go check it out in your browser. Fire up your server. Remember? ./script/server at the root of your Rails application should do it.

The URL will be http://localhost:3000/greetings/hello. I’ll wait for you to be suitably impressed.

“What about data, though?”, you ask over a cup of coffee. Rails comes with a generator for data models too. Can you guess its generator name?

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.

Let’s set up a simple resource called “HighScore” that will keep track of our highest score on video games we play.

Taking it from the top – 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 20081217071914_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.

Let’s see the interface Rails created for us. ./script/server; http://localhost:3000/high_scores

We can create new high scores (55,160 on Space Invaders!)

1.4 console

The console command lets you interact with your Rails application from the command line. On the underside, script/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.

1.5 dbconsole

dbconsolefigures 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.

1.6 plugin

The plugin command simplifies plugin management; think a miniature version of the Gem utility. Let’s walk through installing a plugin. You can call the sub-command discover, which sifts through repositories looking for plugins, or call source to add a specific repository of plugins, or you can specify the plugin location directly.

Let’s say you’re creating a website for a client who wants a small accounting system. Every event having to do with money must be logged, and must never be deleted. Wouldn’t it be great if we could override the behavior of a model to never actually take its record out of the database, but instead, just set a field?

There is such a thing! The plugin we’re installing is called “acts_as_paranoid”, and it lets models implement a “deleted_at” column that gets set when you call destroy. Later, when calling find, the plugin will tack on a database check to filter out “deleted” things.

1.7 runner

runner runs Ruby code in the context of Rails non-interactively. For instance:

1.8 destroy

Think of destroy as the opposite of generate. It’ll figure out what generate did, and undo it. Believe you-me, the creation of this tutorial used this command many times!

1.9 about

Check it: 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! about 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.

2 The Rails Advanced Command Line

The more advanced uses of the command line are focused around finding useful (even surprising at times) options in the utilities, and fitting utilities to your needs and specific work flow. Listed here are some tricks up Rails’ sleeve.

2.1 Rails with Databases and SCM

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. 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 command to generate the basis of your app.

2.2 server with Different Backends

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!).

To use a different server, just install its gem, then use its name for the first parameter to script/server:

2.3 The Rails Generation: Generators

Generators are code that generates code. Let’s experiment by building one. Our generator will generate a text file.

The Rails generator by default looks in these places for available generators, where RAILS_ROOT is the root of your Rails application, like /home/foobar/commandsapp:

• RAILS_ROOT/lib/generators
• RAILS_ROOT/vendor/generators
• Inside any plugin with a directory like “generators” or “rails_generators”
• ~/.rails/generators
• Inside any Gem you have installed with a name ending in “_generator”
• Inside any Gem installed with a “rails_generators” path, and a file ending in “_generator.rb”
• Finally, the builtin Rails generators (controller, model, mailer, etc.)

Let’s try the fourth option (in our home directory), which will be easy to clean up later:

We’ll fill tutorial_test_generator.rb out with:

We take whatever args are supplied, save them to an instance variable, and literally copying from the Rails source, implement a manifest method, which calls record with a block, and we:

• Check there’s a public directory. You bet there is.
• Run the ERb template called “tutorial.erb”.
• Save it into “RAILS_ROOT/public/tutorial.txt”.
• Pass in the arguments we saved through the :assign parameter.

Next we’ll build the template:

Then we’ll make sure it got included in the list of available generators:

SWEET! Now let’s generate some text, yeah!

And the result:

Tada!

2.4 Rake is Ruby Make

Rake is 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.

Let’s take a look at some of these 80 or so rake tasks.

2.4.1 db: Database

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.

2.4.2 doc: Documentation

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.

2.4.3 gems: Ruby gems

You can specify which gems your application uses, and rake gems:install will install them for you. Look at your environment.rb to learn how with the config.gem directive.

2.4.4 notes: Code note enumeration

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.

2.4.5 rails: Rails-specific tasks

In addition to the gems:unpack task above, you can also unpack the Rails backend specific gems into vendor/rails by calling rake rails:freeze:gems, to unpack the version of Rails you are currently using, or rake rails:freeze:edge to unpack the most recent (cutting, bleeding edge) version.

When you have frozen the Rails gems, Rails will prefer to use the code in vendor/rails instead of the system Rails gems. You can “thaw” by running rake rails:unfreeze.

After upgrading Rails, it is useful to run rails:update, which will update your config and scripts directories, and upgrade your Rails-specific javascript (like Scriptaculous).

2.4.6 test: Rails tests

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.

2.4.7 time: Timezones

You can list all the timezones Rails knows about with rake time:zones:all, which is useful just in day-to-day life.

2.4.8 tmp: Temporary files

The tmp directory is, like in 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 an rm -rf * gone awry.

2.4.9 Miscellaneous Tasks

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 psuedo-random key to use for your session secret. 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.

3 Changelog

Lighthouse ticket