ChaptersThis tutorial assumes you have basic Rails knowledge from reading the Getting Started with Rails Guide.
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:
rails consolerails serverrails testrails generaterails db:migraterails db:createrails routesrails dbconsolerails new app_name
You can get a list of rails commands available to you, which will often depend on your current directory, by typing rails --help. Each command has a description, and should help you find the thing you need.
$ rails --help Usage: rails COMMAND [ARGS] The most common rails commands are: generate Generate new code (short-cut alias: "g") console Start the Rails console (short-cut alias: "c") server Start the Rails server (short-cut alias: "s") ... All commands can be run with -h (or --help) for more information. In addition to those commands, there are: about List versions of all Rails ... assets:clean[keep] Remove old compiled assets assets:clobber Remove compiled assets assets:environment Load asset compile environment assets:precompile Compile all the assets ... ... db:fixtures:load Loads fixtures into the ... db:migrate Migrate the database ... db:migrate:status Display status of migrations db:rollback Rolls the schema back to ... db:schema:cache:clear Clears a db/schema_cache.yml file db:schema:cache:dump Creates a db/schema_cache.yml file db:schema:dump Creates a db/schema.rb file ... db:schema:load Loads a schema.rb file ... db:seed Loads the seed data ... db:structure:dump Dumps the database structure ... db:structure:load Recreates the databases ... db:version Retrieves the current schema ... ... restart Restart app by touching ... tmp:create Creates tmp directories ...
Let's create a simple Rails application to step through each of these commands in context.
1.1 rails new
The first thing we'll want to do is create a new Rails application by running the rails new command after installing Rails.
You can install the rails gem by typing gem install rails, if you don't have it already.
$ rails new commandsapp
create
create README.md
create Rakefile
create config.ru
create .gitignore
create Gemfile
create app
...
create tmp/cache
...
run bundle install
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 rails server
The rails server command launches a web server named Puma which comes bundled with Rails. You'll use this any time you want to access your application through a web browser.
With no further work, rails server will run our new shiny Rails app:
$ cd commandsapp $ rails server => Booting Puma => Rails 6.0.0 application starting in development => Run `rails server --help` for more startup options Puma starting in single mode... * Version 3.12.1 (ruby 2.5.7-p206), codename: Llamas in Pajamas * Min threads: 5, max threads: 5 * Environment: development * Listening on tcp://localhost:3000 Use Ctrl-C to stop
With just three commands we whipped up a Rails server listening on port 3000. Go to your browser and open http://localhost:3000, you will see a basic Rails app running.
You can also use the alias "s" to start the server: rails s.
The server can be run on a different port using the -p option. The default development environment can be changed using -e.
$ rails server -e production -p 4000
The -b option binds Rails to the specified IP, by default it is localhost. You can run a server as a daemon by passing a -d option.
1.3 rails generate
The rails generate command uses templates to create a whole lot of things. Running rails generate by itself gives a list of available generators:
You can also use the alias "g" to invoke the generator command: rails g.
$ rails generate Usage: rails generate GENERATOR [args] [options] ... ... Please choose a generator below. Rails: assets channel controller generator ... ...
You can install more generators through generator gems, portions of plugins you'll undoubtedly install, and you can even create your own!
Using generators will save you a large amount of time by writing boilerplate code, code that is necessary for the app to work.
Let's make our own controller with the controller generator. But what command should we use? Let's ask the generator:
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.
$ rails generate controller
Usage: rails generate controller NAME [action action] [options]
...
...
Description:
...
To create a controller within a module, specify the controller name as a path like 'parent_module/controller_name'.
...
Example:
`rails generate controller CreditCards open debit credit close`
Credit card controller with URLs like /credit_cards/debit.
Controller: app/controllers/credit_cards_controller.rb
Test: test/controllers/credit_cards_controller_test.rb
Views: app/views/credit_cards/debit.html.erb [...]
Helper: app/helpers/credit_cards_helper.rb
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.
$ rails generate controller Greetings hello
create app/controllers/greetings_controller.rb
route get 'greetings/hello'
invoke erb
create app/views/greetings
create app/views/greetings/hello.html.erb
invoke test_unit
create test/controllers/greetings_controller_test.rb
invoke helper
create app/helpers/greetings_helper.rb
invoke test_unit
invoke assets
invoke scss
create app/assets/stylesheets/greetings.scss
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.
Check out the controller and modify it a little (in app/controllers/greetings_controller.rb):
class GreetingsController < ApplicationController
def hello
@message = "Hello, how are you today?"
end
end
Then the view, to display our message (in app/views/greetings/hello.html.erb):
<h1>A Greeting for You!</h1> <p><%= @message %></p>
Fire up your server using rails server.
$ rails server => Booting Puma...
The URL will be http://localhost:3000/greetings/hello.
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.
Rails comes with a generator for data models too.
$ rails generate model
Usage:
rails generate model NAME [field[:type][:index] field[:type][:index]] [options]
...
Active Record options:
[--migration] # Indicates when to generate migration
# Default: true
...
Description:
Create rails files for model generator.
For a list of available field types for the type parameter, refer to the API documentation for the add_column method for the SchemaStatements module. The index parameter generates a corresponding index for the column.
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.
We will set up a simple resource called "HighScore" that will keep track of our highest score on video games we play.
$ rails generate scaffold HighScore game:string score:integer
invoke active_record
create db/migrate/20190416145729_create_high_scores.rb
create app/models/high_score.rb
invoke test_unit
create test/models/high_score_test.rb
create test/fixtures/high_scores.yml
invoke resource_route
route resources :high_scores
invoke scaffold_controller
create app/controllers/high_scores_controller.rb
invoke erb
create app/views/high_scores
create app/views/high_scores/index.html.erb
create app/views/high_scores/edit.html.erb
create app/views/high_scores/show.html.erb
create app/views/high_scores/new.html.erb
create app/views/high_scores/_form.html.erb
invoke test_unit
create test/controllers/high_scores_controller_test.rb
create test/system/high_scores_test.rb
invoke helper
create app/helpers/high_scores_helper.rb
invoke test_unit
invoke jbuilder
create app/views/high_scores/index.json.jbuilder
create app/views/high_scores/show.json.jbuilder
create app/views/high_scores/_high_score.json.jbuilder
invoke assets
invoke scss
create app/assets/stylesheets/high_scores.scss
invoke scss
create app/assets/stylesheets/scaffolds.scss
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 20130717151933_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 rails db:migrate command. We'll talk more about that command below.
$ rails db:migrate == CreateHighScores: migrating =============================================== -- create_table(:high_scores) -> 0.0017s == CreateHighScores: migrated (0.0019s) ======================================
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. Please visit the testing guide for an in-depth look at unit testing.
Let's see the interface Rails created for us.
$ rails server
Go to your browser and open http://localhost:3000/high_scores, now we can create new high scores (55,160 on Space Invaders!)
1.4 rails console
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.
You can also use the alias "c" to invoke the console: rails c.
You can specify the environment in which the console command should operate.
$ rails console -e staging
If you wish to test out some code without changing any data, you can do that by invoking rails console --sandbox.
$ rails console --sandbox Loading development environment in sandbox (Rails 5.1.0) Any modifications you make will be rolled back on exit irb(main):001:0>
1.4.1 The app and helper objects
Inside the rails console you have access to the app and helper instances.
With the app method you can access named route helpers, as well as do requests.
>> app.root_path => "/" >> app.get _ Started GET "/" for 127.0.0.1 at 2014-06-19 10:41:57 -0300 ...
With the helper method it is possible to access Rails and your application's helpers.
>> helper.time_ago_in_words 30.days.ago => "about 1 month" >> helper.my_custom_helper => "my custom helper"
1.5 rails dbconsole
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 (including MariaDB), PostgreSQL, and SQLite3.
You can also use the alias "db" to invoke the dbconsole: rails db.
1.6 rails runner
runner runs Ruby code in the context of Rails non-interactively. For instance:
$ rails runner "Model.long_running_method"
You can also use the alias "r" to invoke the runner: rails r.
You can specify the environment in which the runner command should operate using the -e switch.
$ rails runner -e staging "Model.long_running_method"
You can even execute ruby code written in a file with runner.
$ rails runner lib/code_to_be_run.rb
1.7 rails destroy
Think of destroy as the opposite of generate. It'll figure out what generate did, and undo it.
You can also use the alias "d" to invoke the destroy command: rails d.
$ rails generate model Oops
invoke active_record
create db/migrate/20120528062523_create_oops.rb
create app/models/oops.rb
invoke test_unit
create test/models/oops_test.rb
create test/fixtures/oops.yml
$ rails destroy model Oops
invoke active_record
remove db/migrate/20120528062523_create_oops.rb
remove app/models/oops.rb
invoke test_unit
remove test/models/oops_test.rb
remove test/fixtures/oops.yml
1.8 rails about
rails about 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.
$ rails about About your application's environment Rails version 6.0.0 Ruby version 2.5.0 (x86_64-linux) RubyGems version 2.7.3 Rack version 2.0.4 JavaScript Runtime Node.js (V8) Middleware: Rack::Sendfile, ActionDispatch::Static, ActionDispatch::Executor, ActiveSupport::Cache::Strategy::LocalCache::Middleware, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, ActionDispatch::RemoteIp, Sprockets::Rails::QuietAssets, Rails::Rack::Logger, ActionDispatch::ShowExceptions, WebConsole::Middleware, ActionDispatch::DebugExceptions, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, Rack::Head, Rack::ConditionalGet, Rack::ETag Application root /home/foobar/commandsapp Environment development Database adapter sqlite3 Database schema version 20180205173523
1.9 rails assets:
You can precompile the assets in app/assets using rails assets:precompile, and remove older compiled assets using rails assets:clean. The assets:clean command allows for rolling deploys that may still be linking to an old asset while the new assets are being built.
If you want to clear public/assets completely, you can use rails assets:clobber.
1.10 rails db:
The most common commands of the db: rails namespace are migrate and create, and it will pay off to try out all of the migration rails commands (up, down, redo, reset). rails db:version is useful when troubleshooting, telling you the current version of the database.
More information about migrations can be found in the Migrations guide.
1.11 rails notes
rails notes searches through your code for comments beginning with a specific keyword. You can refer to rails notes --help for information about usage.
By default, it will search in app, config, db, lib, and test directories for FIXME, OPTIMIZE, and TODO annotations in files with extension .builder, .rb, .rake, .yml, .yaml, .ruby, .css, .js, and .erb.
$ rails notes app/controllers/admin/users_controller.rb: * [ 20] [TODO] any other way to do this? * [132] [FIXME] high priority for next deploy lib/school.rb: * [ 13] [OPTIMIZE] refactor this code to make it faster * [ 17] [FIXME]
1.11.1 Annotations
You can pass specific annotations by using the --annotations argument. By default, it will search for FIXME, OPTIMIZE, and TODO.
Note that annotations are case sensitive.
$ rails notes --annotations FIXME RELEASE app/controllers/admin/users_controller.rb: * [101] [RELEASE] We need to look at this before next release * [132] [FIXME] high priority for next deploy lib/school.rb: * [ 17] [FIXME]
1.11.2 Tags
You can add more default tags to search for by using config.annotations.register_tags. It receives a list of tags.
config.annotations.register_tags("DEPRECATEME", "TESTME")
$ rails notes app/controllers/admin/users_controller.rb: * [ 20] [TODO] do A/B testing on this * [ 42] [TESTME] this needs more functional tests * [132] [DEPRECATEME] ensure this method is deprecated in next release
1.11.3 Directories
You can add more default directories to search from by using config.annotations.register_directories. It receives a list of directory names.
config.annotations.register_directories("spec", "vendor")
$ rails notes app/controllers/admin/users_controller.rb: * [ 20] [TODO] any other way to do this? * [132] [FIXME] high priority for next deploy lib/school.rb: * [ 13] [OPTIMIZE] Refactor this code to make it faster * [ 17] [FIXME] spec/models/user_spec.rb: * [122] [TODO] Verify the user that has a subscription works vendor/tools.rb: * [ 56] [TODO] Get rid of this dependency
1.11.4 Extensions
You can add more default file extensions to search from by using config.annotations.register_extensions. It receives a list of extensions with its corresponding regex to match it up.
config.annotations.register_extensions("scss", "sass") { |annotation| /\/\/\s*(#{annotation}):?\s*(.*)$/ }
$ rails notes app/controllers/admin/users_controller.rb: * [ 20] [TODO] any other way to do this? * [132] [FIXME] high priority for next deploy app/assets/stylesheets/application.css.sass: * [ 34] [TODO] Use pseudo element for this class app/assets/stylesheets/application.css.scss: * [ 1] [TODO] Split into multiple components lib/school.rb: * [ 13] [OPTIMIZE] Refactor this code to make it faster * [ 17] [FIXME] spec/models/user_spec.rb: * [122] [TODO] Verify the user that has a subscription works vendor/tools.rb: * [ 56] [TODO] Get rid of this dependency
1.12 rails routes
rails 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.
1.13 rails test
A good description of unit testing in Rails is given in A Guide to Testing Rails Applications
Rails comes with a test framework called minitest. Rails owes its stability to the use of tests. The commands available in the test: namespace helps in running the different tests you will hopefully write.
1.14 rails tmp:
The Rails.root/tmp directory is, like the *nix /tmp directory, the holding place for temporary files like process id files and cached actions.
The tmp: namespaced commands will help you clear and create the Rails.root/tmp directory:
-
rails tmp:cache:clearclearstmp/cache. -
rails tmp:sockets:clearclearstmp/sockets. -
rails tmp:screenshots:clearclearstmp/screenshots. -
rails tmp:clearclears all cache, sockets, and screenshot files. -
rails tmp:createcreates tmp directories for cache, sockets, and pids.
1.15 Miscellaneous
-
rails statsis great for looking at statistics on your code, displaying things like KLOCs (thousands of lines of code) and your code to test ratio. -
rails secretwill give you a pseudo-random key to use for your session secret. -
rails time:zones:alllists all the timezones Rails knows about.
1.16 Custom Rake Tasks
Custom rake tasks have a .rake extension and are placed in
Rails.root/lib/tasks. You can create these custom rake tasks with the
rails generate task command.
desc "I am short, but comprehensive description for my cool task" task task_name: [:prerequisite_task, :another_task_we_depend_on] do # All your magic here # Any valid Ruby code is allowed end
To pass arguments to your custom rake task:
task :task_name, [:arg_1] => [:prerequisite_1, :prerequisite_2] do |task, args| argument_1 = args.arg_1 end
You can group tasks by placing them in namespaces:
namespace :db do
desc "This task does nothing"
task :nothing do
# Seriously, nothing
end
end
Invocation of the tasks will look like:
$ rails task_name $ rails "task_name[value 1]" # entire argument string should be quoted $ rails db:nothing
If you need to interact with your application models, perform database queries, and so on, your task should depend on the environment task, which will load your application code.
2 The Rails Advanced Command Line
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.
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:
$ mkdir gitapp
$ cd gitapp
$ git init
Initialized empty Git repository in .git/
$ rails new . --git --database=postgresql
exists
create app/controllers
create app/helpers
...
...
create tmp/cache
create tmp/pids
create Rakefile
add 'Rakefile'
create README.md
add 'README.md'
create app/controllers/application_controller.rb
add 'app/controllers/application_controller.rb'
create app/helpers/application_helper.rb
...
create log/test.log
add 'log/test.log'
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:
$ cat config/database.yml
# PostgreSQL. Versions 9.1 and up are supported.
#
# Install the pg driver:
# gem install pg
# On macOS with Homebrew:
# gem install pg -- --with-pg-config=/usr/local/bin/pg_config
# On macOS with MacPorts:
# gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
# gem install pg
# Choose the win32 build.
# Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
default: &default
adapter: postgresql
encoding: unicode
# For details on connection pooling, see Rails configuration guide
# https://guides.rubyonrails.org/configuring.html#database-pooling
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
development:
<<: *default
database: gitapp_development
...
...
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 new command to generate the basis of your app.
Feedback
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Please contribute if you see any typos or factual errors. To get started, you can read our documentation contributions section.
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If for whatever reason you spot something to fix but cannot patch it yourself, please open an issue.
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