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← Avvo Coding Styleguides

Avvo Rails Style Guide

A mostly reasonable approach to Ruby on Rails

(forked from bbatsov's style guide)

Table of Contents

Developing Rails applications

Configuration

  • Put custom initialization code in config/initializers. The code in initializers executes on application startup.

  • Keep initialization code for each gem in a separate file with the same name as the gem, for example carrierwave.rb, active_admin.rb, etc.

  • Adjust accordingly the settings for development, test and production environment (in the corresponding files under config/environments/)

    • Mark additional assets for precompilation (if any):

      ```Ruby
# config/environments/production.rb
# Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added)
config.assets.precompile += %w( rails_admin/rails_admin.css rails_admin/rails_admin.js )
```

  • Keep configuration that's applicable to all environments in the config/application.rb file.

Routing

  • When you need to add more actions to a RESTful resource (do you really need them at all?) use member and collection routes.

    # bad
get 'subscriptions/:id/unsubscribe'
resources :subscriptions

# good
resources :subscriptions do
  get 'unsubscribe', on: :member
end

# bad
get 'photos/search'
resources :photos

# good
resources :photos do
  get 'search', on: :collection
end

  • If you need to define multiple member/collection routes use the alternative block syntax.

    resources :subscriptions do
  member do
    get 'unsubscribe'
    # more routes
  end
end

resources :photos do
  collection do
    get 'search'
    # more routes
  end
end

  • Use nested routes to express better the relationship between ActiveRecord models.

    class Post < ActiveRecord::Base
  has_many :comments
end

class Comments < ActiveRecord::Base
  belongs_to :post
end

# routes.rb
resources :posts do
  resources :comments
end

  • Use namespaced routes to group related actions.

    namespace :admin do
  # Directs /admin/products/* to Admin::ProductsController
  # (app/controllers/admin/products_controller.rb)
  resources :products
end

  • Never use the legacy wild controller route. This route will make all actions in every controller accessible via GET requests.

    # very bad
match ':controller(/:action(/:id(.:format)))'

  • Don't use match to define any routes. It's removed from Rails 4.

Controllers

  • Keep the controllers skinny - they should only retrieve data for the view layer and shouldn't contain any business logic (all the business logic should naturally reside in the model).
  • Each controller action should (ideally) invoke only one method other than an initial find or new.
  • Share no more than two instance variables between a controller and a view.

Models

  • Introduce non-ActiveRecord model classes freely.

  • Name the models with meaningful (but short) names without abbreviations.

  • If you need model objects that support ActiveRecord behavior(like validation) use the ActiveAttr gem.

    class Message
  include ActiveAttr::Model

  attribute :name
  attribute :email
  attribute :content
  attribute :priority

  attr_accessible :name, :email, :content

  validates :name, presence: true
  validates :email, format: { with: /\A[-a-z0-9_+\.]+\@([-a-z0-9]+\.)+[a-z0-9]{2,4}\z/i }
  validates :content, length: { maximum: 500 }
end

    For a more complete example refer to the RailsCast on the subject.

ActiveRecord

  • Avoid altering ActiveRecord defaults (table names, primary key, etc) unless you have a very good reason (like a database that's not under your control).

    # bad - don't do this if you can modify the schema
class Transaction < ActiveRecord::Base
  self.table_name = 'order'
  ...
end

  • Group macro-style methods (has_many, validates, etc) in the beginning of the class definition.

    class User < ActiveRecord::Base
  # keep the default scope first (if any)
  default_scope { where(active: true) }

  # constants come up next
  GENDERS = %w(male female)

  # afterwards we put attr related macros
  attr_accessor :formatted_date_of_birth

  attr_accessible :login, :first_name, :last_name, :email, :password

  # followed by association macros
  belongs_to :country

  has_many :authentications, dependent: :destroy

  # and validation macros
  validates :email, presence: true
  validates :username, presence: true
  validates :username, uniqueness: { case_sensitive: false }
  validates :username, format: { with: /\A[A-Za-z][A-Za-z0-9._-]{2,19}\z/ }
  validates :password, format: { with: /\A\S{8,128}\z/, allow_nil: true}

  # next we have callbacks
  before_save :cook
  before_save :update_username_lower

  # other macros (like devise's) should be placed after the callbacks

  ...
end

  • Prefer has_many :through to has_and_belongs_to_many. Using has_many :through allows additional attributes and validations on the join model.

    # using has_and_belongs_to_many
class User < ActiveRecord::Base
  has_and_belongs_to_many :groups
end

class Group < ActiveRecord::Base
  has_and_belongs_to_many :users
end

# prefered way - using has_many :through
class User < ActiveRecord::Base
  has_many :memberships
  has_many :groups, through: :memberships
end

class Membership < ActiveRecord::Base
  belongs_to :user
  belongs_to :group
end

class Group < ActiveRecord::Base
  has_many :memberships
  has_many :users, through: :memberships
end

  • Prefer self[:attribute] over read_attribute(:attribute).

    # bad
def amount
  read_attribute(:amount) * 100
end

# good
def amount
  self[:amount] * 100
end

  • Always use the new "sexy" validations.

    # bad
validates_presence_of :email

# good
validates :email, presence: true

  • When a custom validation is used more than once or the validation is some regular expression mapping, create a custom validator file.

    # bad
class Person
  validates :email, format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i }
end

# good
class EmailValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    record.errors[attribute] << (options[:message] || 'is not a valid email') unless value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
  end
end

class Person
  validates :email, email: true
end

  • Keep custom validators under app/validators.

  • Consider extracting custom validators to a shared gem if you're maintaining several related apps or the validators are generic enough.

  • Use named scopes freely.

    class User < ActiveRecord::Base
  scope :active, -> { where(active: true) }
  scope :inactive, -> { where(active: false) }

  scope :with_orders, -> { joins(:orders).select('distinct(users.id)') }
end

  • Wrap named scopes in lambdas to initialize them lazily (this is only a prescription in Rails 3, but is mandatory in Rails 4).

    # bad
class User < ActiveRecord::Base
  scope :active, where(active: true)
  scope :inactive, where(active: false)

  scope :with_orders, joins(:orders).select('distinct(users.id)')
end

# good
class User < ActiveRecord::Base
  scope :active, -> { where(active: true) }
  scope :inactive, -> { where(active: false) }

  scope :with_orders, -> { joins(:orders).select('distinct(users.id)') }
end

  • When a named scope defined with a lambda and parameters becomes too complicated, it is preferable to make a class method instead which serves the same purpose of the named scope and returns an ActiveRecord::Relation object. Arguably you can define even simpler scopes like this.

    class User < ActiveRecord::Base
  def self.with_orders
    joins(:orders).select('distinct(users.id)')
  end
end

  • Beware of the behavior of the update_attribute method. It doesn't run the model validations (unlike update_attributes) and could easily corrupt the model state. The method was finally deprecated in Rails 3.2.7 and does not exist in Rails 4.

  • Use user-friendly URLs. Show some descriptive attribute of the model in the URL rather than its id. There is more than one way to achieve this:

    • Override the to_param method of the model. This method is used by Rails for constructing a URL to the object. The default implementation returns the id of the record as a String. It could be overridden to include another human-readable attribute.

      ```Ruby
class Person
  def to_param
    "#{id} #{name}".parameterize
  end
end
```

      In order to convert this to a URL-friendly value, parameterize should be called on the string. The id of the object needs to be at the beginning so that it can be found by the find method of ActiveRecord.

    • Use the friendly_id gem. It allows creation of human-readable URLs by using some descriptive attribute of the model instead of its id.

      ```Ruby
class Person
  extend FriendlyId
  friendly_id :name, use: :slugged
end
```

    Check the gem documentation for more information about its usage.

  • Use find_each to iterate over a collection of AR objects. Looping through a collection of records from the database (using the all method, for example) is very inefficient since it will try to instantiate all the objects at once. In that case, batch processing methods allow you to work with the records in batches, thereby greatly reducing memory consumption.

    # bad
Person.all.each do |person|
  person.do_awesome_stuff
end

Person.where("age > 21").each do |person|
  person.party_all_night!
end

# good
Person.all.find_each do |person|
  person.do_awesome_stuff
end

Person.where("age > 21").find_each do |person|
  person.party_all_night!
end

Migrations

  • Keep the schema.rb (or structure.sql) under version control.

  • Use rake db:schema:load instead of rake db:migrate to initialize an empty database.

  • Use rake db:test:prepare to update the schema of the test database.

  • Enforce default values in the migrations themselves instead of in the application layer.

    # bad - application enforced default value
def amount
  self[:amount] or 0
end

    While enforcing table defaults only in Rails is suggested by many Rails developers, it's an extremely brittle approach that leaves your data vulnerable to many application bugs. And you'll have to consider the fact that most non-trivial apps share a database with other applications, so imposing data integrity from the Rails app is impossible.

  • Enforce foreign-key constraints. While ActiveRecord does not support them natively, there some great third-party gems like schema_plus and foreigner.

  • Don't use model classes in migrations. The model classes are constantly evolving and at some point in the future migrations that used to work might stop, because of changes in the models used.

Views

  • Avoid calling the model layer directly from a view.
  • Never make complex formatting in the views, export the formatting to a method in the view helper or the model.
  • Mitigate code duplication by using partial templates and layouts.

Internationalization

  • No strings or other locale specific settings should be used in the views, models and controllers. These texts should be moved to the locale files in the config/locales directory.

  • When the labels of an ActiveRecord model need to be translated, use the activerecord scope:

    en:
  activerecord:
    models:
      user: Member
    attributes:
      user:
        name: "Full name"

    Then User.model_name.human will return "Member" and User.human_attribute_name("name") will return "Full name". These translations of the attributes will be used as labels in the views.

  • Place the shared localization options, such as date or currency formats, in files under the root of the locales directory.

  • Use the short form of the I18n methods: I18n.t instead of I18n.translate and I18n.l instead of I18n.localize.

  • Use "lazy" lookup for the texts used in views. Let's say we have the following structure:

    en:
  users:
    show:
      title: "User details page"

    The value for users.show.title can be looked up in the template app/views/users/show.html.haml like this:

    = t '.title'

  • Use the dot-separated keys in the controllers and models instead of specifying the :scope option. The dot-separated call is easier to read and trace the hierarchy.

    # use this call
I18n.t 'activerecord.errors.messages.record_invalid'

# instead of this
I18n.t :record_invalid, :scope => [:activerecord, :errors, :messages]

  • More detailed information about the Rails i18n can be found in the [Rails Guides] (http://guides.rubyonrails.org/i18n.html)

Assets

Use the assets pipeline to leverage organization within your application.

  • Reserve app/assets for custom stylesheets, javascripts, or images.
  • Use lib/assets for your own libraries, that doesn’t really fit into the scope of the application.
  • Third party code such as jQuery or bootstrap should be placed in vendor/assets.
  • When possible, use gemified versions of assets (e.g. jquery-rails, jquery-ui-rails, bootstrap-sass, zurb-foundation).

Bundler

  • Put gems used only for development or testing in the appropriate group in the Gemfile.

  • Use only established gems in your projects. If you're contemplating on including some little-known gem you should do a careful review of its source code first.

  • OS-specific gems will by default result in a constantly changing Gemfile.lock for projects with multiple developers using different operating systems. Add all OS X specific gems to a darwin group in the Gemfile, and all Linux specific gems to a linux group:

    # Gemfile
group :darwin do
  gem 'rb-fsevent'
  gem 'growl'
end

group :linux do
  gem 'rb-inotify'
end

    To require the appropriate gems in the right environment, add the following to config/application.rb:

    platform = RUBY_PLATFORM.match(/(linux|darwin)/)[0].to_sym
Bundler.require(platform)

  • Do not remove the Gemfile.lock from version control. This is not some randomly generated file - it makes sure that all of your team members get the same gem versions when they do a bundle install.

Gems

Here's a list of some "priceless" gems that we use at Avvo:

  • better_errors - Better Errors replaces the standard Rails error page with a much better and more useful error page. It is also usable outside of Rails in any Rack app as Rack middleware.

  • capybara - Capybara aims to simplify the process of integration testing Rack applications, such as Rails, Sinatra or Merb. Capybara simulates how a real user would interact with a web application. It is agnostic about the driver running your tests and currently comes with Rack::Test and Selenium support built in. HtmlUnit, WebKit and env.js are supported through external gems.

  • carrierwave - the ultimate file upload solution for Rails. Support both local and cloud storage for the uploaded files (and many other cool things). Integrates great with ImageMagick for image post-processing.

  • compass-rails - Great gem that adds support for some css frameworks. Includes collection of sass mixins that reduces code of css files and help fight with browser incompatibilities.

  • factory_girl - Nice and mature fixture replacement. Spiritual ancestor of fabrication.

  • kaminari - Great paginating solution.

  • simplecov - code coverage tool; generates great reports.

  • simplecov-rcov - RCov formatter for SimpleCov. Useful if you're trying to use SimpleCov with the Hudson contininous integration server.

  • slim - Slim is a concise templating language, considered by many far superior to HAML (not to mention Erb). Its performance is phenomenal.

This list is not exhaustive and other gems might be added to it along the road. All of the gems on the list are field tested, have active development and community and are known to be of good code quality.

Flawed Gems

This is a list of gems that are either problematic or superseded by other gems. You should avoid using them in your projects.

  • rmagick - this gem is notorious for its memory consumption. Use minimagick instead.
  • autotest - old solution for running tests automatically. Far inferior to guard and watchr.
  • rcov - code coverage tool, not compatible with Ruby 1.9. Use SimpleCov instead.
  • therubyracer - the use of this gem in production is strongly discouraged as it uses a very large amount of memory. I'd suggest using node.js instead.

This list is also a work in progress. Please, let me know if you know other popular, but flawed gems.

Managing processes

  • If your projects depends on various external processes use foreman to manage them.

Testing Rails applications

needs documentation

License

Creative Commons License This work is licensed under a Creative Commons Attribution 3.0 Unported License

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