rails style guide

:green_book: Russian Version: A community-driven Rails 3 & 4 & 5 style guide.

arbox
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Ruby

Prelude

Role models are important.

– Officer Alex J. Murphy / RoboCop

The goal of this guide is to present a set of best practices and style
prescriptions for Ruby on Rails 4 development. It’s a
complementary guide to the already existing community-driven
Ruby coding style guide.

Some of the advice here is applicable only to Rails 4.0+.

You can generate a PDF or an HTML copy of this guide using
Pandoc.

Translations of the guide are available in the following languages:

The Rails Style Guide

This Rails style guide recommends best practices so that real-world Rails
programmers can write code that can be maintained by other real-world Rails
programmers. A style guide that reflects real-world usage gets used, and a
style guide that holds to an ideal that has been rejected by the people it
is supposed to help risks not getting used at all – no matter how good
it is.

The guide is separated into several sections of related rules. I’ve tried to add
the rationale behind the rules (if it’s omitted I’ve assumed it’s pretty
obvious).

I didn’t come up with all the rules out of nowhere - they are mostly based on my
extensive career as a professional software engineer, feedback and suggestions
from members of the Rails community and various highly regarded Rails
programming resources.

Table of Contents

Configuration


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


  • 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.
    [link]


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

    • Mark additional assets for precompilation (if any):

      # 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.
    [link]


  • Create an additional staging environment that closely resembles the
    production one.
    [link]


  • Keep any additional configuration in YAML files under the config/ directory.
    [link]

    Since Rails 4.2 YAML configuration files can be easily loaded with the new config_for method:

    Rails::Application.config_for(:yaml_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.
    [link]

    # 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.
    [link]

    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.
    [link]

    class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

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


  • If you need to nest routes more than 1 level deep then use the shallow: true option. This will save user from long urls posts/1/comments/5/versions/7/edit and you from long url helpers edit_post_comment_version.

    resources :posts, shallow: true do
  resources :comments do
    resources :versions
  end
end


  • Use namespaced routes to group related actions.
    [link]

    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.
    [link]

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


  • Don’t use match to define any routes unless there is need to map multiple request types among [:get, :post, :patch, :put, :delete] to a single action using :via option.
    [link]

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).
    [link]


  • Each controller action should (ideally) invoke only one method other than an
    initial find or new.
    [link]


  • Share no more than two instance variables between a controller and a view.
    [link]


  • Controller actions specified in the option of Action Filter should be in lexical scope. The ActionFilter specified for an inherited action makes it difficult to understand the scope of its impact on that action.
    [link]

# bad
class UsersController < ApplicationController
  before_action :require_login, only: :export
end

# good
class UsersController < ApplicationController
  before_action :require_login, only: :export

  def export
  end
end

Rendering


  • Prefer using a template over inline rendering.
    [link]
# very bad
class ProductsController < ApplicationController
  def index
    render inline: "<% products.each do |p| %><p><%= p.name %></p><% end %>", type: :erb
  end
end

# good
## app/views/products/index.html.erb
<%= render partial: 'product', collection: products %>

## app/views/products/_product.html.erb
<p><%= product.name %></p>
<p><%= product.price %></p>

## app/controllers/foo_controller.rb
class ProductsController < ApplicationController
  def index
    render :index
  end
end

  • Prefer render plain: over render text:.
    [link]
# bad - sets MIME type to `text/html`
...
render text: 'Ruby!'
...

# bad - requires explicit MIME type declaration
...
render text: 'Ruby!', content_type: 'text/plain'
...

# good - short and precise
...
render plain: 'Ruby!'
...

  • Prefer corresponding symbols to numeric HTTP status codes. They are meaningful and do not look like “magic” numbers for less known HTTP status codes.
    [link]
# bad
...
render status: 403
...

# good
...
render status: :forbidden
...

Models


  • Introduce non-ActiveRecord model classes freely.
    [link]


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


  • If you need model objects that support ActiveRecord behavior (like validation)
    without the ActiveRecord database functionality use the
    ActiveAttr gem.
    [link]

    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.


  • Unless they have some meaning in the business domain, don’t put methods in
    your model that just format your data (like code generating HTML). These
    methods are most likely going to be called from the view layer only, so their
    place is in helpers. Keep your models for business logic and data-persistence
    only.
    [link]

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).
    [link]

    # 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.
    [link]

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

  # constants come up next
  COLORS = %w(red green blue)

  # afterwards we put attr related macros
  attr_accessor :formatted_date_of_birth

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

  # Rails4+ enums after attr macros, prefer the hash syntax
  enum gender: { female: 0, male: 1 }

  # 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.
    [link]

    # not so good - 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

# preferred 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).
    [link]

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

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


  • Prefer self[:attribute] = value over write_attribute(:attribute, value).
    [link]

    # bad
def amount
  write_attribute(:amount, 100)
end

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


  • Always use the new “sexy”
    validations    .
    [link]

    # bad
validates_presence_of :email
validates_length_of :email, maximum: 100

# good
validates :email, presence: true, length: { maximum: 100 }


  • To make validations easy to read, don’t list multiple attributes per
    validation
    [link]

    # bad
validates :email, :password, presence: true
validates :email, length: { maximum: 100 }

# good
validates :email, presence: true, length: { maximum: 100 }
validates :password, presence: true


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

    # 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.
    [link]


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


  • Use named scopes freely.
    [link]

    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.
    [link]

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


  • Order callback declarations in the order, in which they will be executed. For
    referenece, see Available Callbacks
    [link]

    #bad
class Person
  after_commit/after_rollback :after_commit_callback
  after_save :after_save_callback
  around_save :around_save_callback
  after_update :after_update_callback
  before_update :before_update_callback
  after_validation :after_validation_callback
  before_validation :before_validation_callback
  before_save :before_save_callback
  before_create :before_create_callback
  after_create :after_create_callback
  around_create :around_create_callback
  around_update :around_update_callback
end

#good
class Person
  before_validation :before_validation_callback
  after_validation :after_validation_callback
  before_save :before_save_callback
  around_save :around_save_callback
  before_create :before_create_callback
  around_create :around_create_callback
  after_create :after_create_callback
  before_update :before_update_callback
  around_update :around_update_callback
  after_update :after_update_callback
  after_save :after_save_callback
  after_commit/after_rollback :after_commit_callback
end


  • Beware of the behavior of the
    following
    methods. They do not run the model validations and
    could easily corrupt the model state.
    [link]

    # bad
Article.first.decrement!(:view_count)
DiscussionBoard.decrement_counter(:post_count, 5)
Article.first.increment!(:view_count)
DiscussionBoard.increment_counter(:post_count, 5)
person.toggle :active
product.touch
Billing.update_all("category = 'authorized', author = 'David'")
user.update_attribute(:website, 'example.com')
user.update_columns(last_request_at: Time.current)
Post.update_counters 5, comment_count: -1, action_count: 1

# good
user.update_attributes(website: 'example.com')


  • 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:
    [link]

    • 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.

      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.

      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.
    [link]

    # 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.find_each do |person|
  person.do_awesome_stuff
end

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


  • Since Rails creates callbacks for dependent
    associations    , always call
    before_destroy callbacks that perform validation with prepend: true.
    [link]

    # bad (roles will be deleted automatically even if super_admin? is true)
has_many :roles, dependent: :destroy

before_destroy :ensure_deletable

def ensure_deletable
  raise "Cannot delete super admin." if super_admin?
end

# good
has_many :roles, dependent: :destroy

before_destroy :ensure_deletable, prepend: true

def ensure_deletable
  raise "Cannot delete super admin." if super_admin?
end


  • Define the dependent option to the has_many and has_one associations.
    [link]

    # bad
class Post < ActiveRecord::Base
  has_many :comments
end

# good
class Post < ActiveRecord::Base
  has_many :comments, dependent: :destroy
end


  • When persisting AR objects always use the exception raising bang! method or handle the method return value.
    This applies to create, save, update, destroy, first_or_create and find_or_create_by.
    [link]

    # bad
user.create(name: 'Bruce')

# bad
user.save

# good
user.create!(name: 'Bruce')
# or
bruce = user.create(name: 'Bruce')
if bruce.persisted?
  ...
else
  ...
end

# good
user.save!
# or
if user.save
  ...
else
  ...
end

ActiveRecord Queries


  • Avoid string interpolation in
    queries, as it will make your code susceptible to SQL injection
    attacks.
    [link]

    # bad - param will be interpolated unescaped
Client.where("orders_count = #{params[:orders]}")

# good - param will be properly escaped
Client.where('orders_count = ?', params[:orders])


  • Consider using named placeholders instead of positional placeholders
    when you have more than 1 placeholder in your query.
    [link]

    # okish
Client.where(
  'created_at >= ? AND created_at <= ?',
  params[:start_date], params[:end_date]
)

# good
Client.where(
  'created_at >= :start_date AND created_at <= :end_date',
  start_date: params[:start_date], end_date: params[:end_date]
)


  • Favor the use of find over where.take!, find_by!, and find_by_id!
    when you need to retrieve a single record by primary key id and raise
    ActiveRecord::RecordNotFound when the record is not found.
    [link]

    # bad
User.where(id: id).take!

# bad
User.find_by_id!(id)

# bad
User.find_by!(id: id)

# good
User.find(id)


  • Favor the use of find_by over where.take and find_by_attribute
    when you need to retrieve a single record by one or more attributes and return
    nil when the record is not found.
    [link]

    # bad
User.where(id: id).take
User.where(first_name: 'Bruce', last_name: 'Wayne').take

# bad
User.find_by_id(id)
# bad, deprecated in ActiveRecord 4.0, removed in 4.1+
User.find_by_first_name_and_last_name('Bruce', 'Wayne')

# good
User.find_by(id: id)
User.find_by(first_name: 'Bruce', last_name: 'Wayne')


  • Favor the use of where.not over SQL.
    [link]

    # bad
User.where("id != ?", id)

# good
User.where.not(id: id)


  • Don’t use the id column for ordering. The sequence of ids is not
    guaranteed to be in any particular order, despite often (incidentally)
    being chronological. Use a timestamp column to order chronologically.
    As a bonus the intent is clearer.
    [link]

    # bad
scope :chronological, -> { order(id: :asc) }

# good
scope :chronological, -> { order(created_at: :asc) }


  • Favor the use of ids over pluck(:id).
    [link]

    # bad
User.pluck(:id)

# good
User.ids


  • When specifying an explicit query in a method such as find_by_sql, use
    heredocs with squish. This allows you to legibly format the SQL with
    line breaks and indentations, while supporting syntax highlighting in many
    tools (including GitHub, Atom, and RubyMine).
    [link]

    User.find_by_sql(<<-SQL.squish)
  SELECT
    users.id, accounts.plan
  FROM
    users
  INNER JOIN
    accounts
  ON
    accounts.user_id = users.id
  # further complexities...
SQL

    String#squish removes the indentation and newline characters so that your server
    log shows a fluid string of SQL rather than something like this:

    SELECT\n    users.id, accounts.plan\n  FROM\n    users\n  INNER JOIN\n    acounts\n  ON\n    accounts.user_id = users.id


  • When querying ActiveRecord collections, prefer size (selects between count/length behavior based on whether collection is already loaded) or length (always loads the whole collection and counts the array elements) over count (always does a database query for the count).
    [link]

    # bad
User.count

# good
User.all.size

# good - if you really need to load all users into memory
User.all.length

Migrations


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


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


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

    # bad - application enforced default value
class Product < ActiveRecord::Base
  def amount
    self[:amount] || 0
  end
end

# good - database enforced
class AddDefaultAmountToProducts < ActiveRecord::Migration
  def change
    change_column_default :products, :amount, 0
  end
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. As of Rails 4.2, ActiveRecord
    supports foreign key constraints natively.
    [link]


  • When writing constructive migrations (adding tables or columns),
    use the change method instead of up and down methods.
    [link]

    # the old way
class AddNameToPeople < ActiveRecord::Migration
  def up
    add_column :people, :name, :string
  end

  def down
    remove_column :people, :name
  end
end

# the new preferred way
class AddNameToPeople < ActiveRecord::Migration
  def change
    add_column :people, :name, :string
  end
end


  • If you have to use models in migrations, make sure you define them
    so that you don’t end up with broken migrations in the future
    [link]

    # db/migrate/<migration_file_name>.rb
# frozen_string_literal: true

# bad
class ModifyDefaultStatusForProducts < ActiveRecord::Migration
  def change
    old_status = 'pending_manual_approval'
    new_status = 'pending_approval'

    reversible do |dir|
      dir.up do
        Product.where(status: old_status).update_all(status: new_status)
        change_column :products, :status, :string, default: new_status
      end

      dir.down do
        Product.where(status: new_status).update_all(status: old_status)
        change_column :products, :status, :string, default: old_status
      end
    end
  end
end

# good
# Define `table_name` in a custom named class to make sure that
# you run on the same table you had during the creation of the migration.
# In future if you override the `Product` class
# and change the `table_name`, it won't break
# the migration or cause serious data corruption.
class MigrationProduct < ActiveRecord::Base
  self.table_name = :products
end

class ModifyDefaultStatusForProducts < ActiveRecord::Migration
  def change
    old_status = 'pending_manual_approval'
    new_status = 'pending_approval'

    reversible do |dir|
      dir.up do
        MigrationProduct.where(status: old_status).update_all(status: new_status)
        change_column :products, :status, :string, default: new_status
      end

      dir.down do
        MigrationProduct.where(status: new_status).update_all(status: old_status)
        change_column :products, :status, :string, default: old_status
      end
    end
  end
end


  • Name your foreign keys explicitly instead of relying on Rails auto-generated
    FK names. (http://guides.rubyonrails.org/active_record_migrations.html#foreign-keys)
    [link]

    # bad
class AddFkArticlesToAuthors < ActiveRecord::Migration
  def change
    add_foreign_key :articles, :authors
  end
end

# good
class AddFkArticlesToAuthors < ActiveRecord::Migration
  def change
    add_foreign_key :articles, :authors, name: :articles_author_id_fk
  end
end


  • Don’t use non-reversible migration commands in the change method.
    Reversible migration commands are listed below.
    ActiveRecord::Migration::CommandRecorder
    [link]

    # bad
class DropUsers < ActiveRecord::Migration
  def change
    drop_table :users
  end
end

# good
class DropUsers < ActiveRecord::Migration
  def up
    drop_table :users
  end

  def down
    create_table :users do |t|
      t.string :name
    end
  end
end

# good
# In this case, block will be used by create_table in rollback
# http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters.html#method-i-drop_table
class DropUsers < ActiveRecord::Migration
  def change
    drop_table :users do |t|
      t.string :name
    end
  end
end

Views


  • Never call the model layer directly from a view.
    [link]


  • Never make complex formatting in the views, export the formatting to a method
    in the view helper or the model.
    [link]


  • Mitigate code duplication by using partial templates and layouts.
    [link]

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.
    [link]


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

    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.


  • Separate the texts used in the views from translations of ActiveRecord
    attributes. Place the locale files for the models in a folder locales/models and the
    texts used in the views in folder locales/views.
    [link]

    • When organization of the locale files is done with additional directories,
      these directories must be described in the application.rb file in order
      to be loaded.

      # config/application.rb
config.i18n.load_path += Dir[Rails.root.join('config', 'locales', '**', '*.{rb,yml}')]


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


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


  • Use “lazy” lookup for the texts used in views. Let’s say we have the following
    structure:
    [link]

    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.
    [link]

    # bad
I18n.t :record_invalid, scope: [:activerecord, :errors, :messages]

# good
I18n.t 'activerecord.errors.messages.record_invalid'


  • More detailed information about the Rails I18n can be found in the Rails
    Guides
    [link]

Assets

Use the assets pipeline to leverage organization within
your application.

Mailers


  • Name the mailers SomethingMailer. Without the Mailer suffix it isn’t
    immediately apparent what’s a mailer and which views are related to the
    mailer.
    [link]


  • Provide both HTML and plain-text view templates.
    [link]


  • Enable errors raised on failed mail delivery in your development environment.
    The errors are disabled by default.
    [link]

    # config/environments/development.rb

config.action_mailer.raise_delivery_errors = true


  • Use a local SMTP server like
    Mailcatcher in the development
    environment.
    [link]

    # config/environments/development.rb

config.action_mailer.smtp_settings = {
  address: 'localhost',
  port: 1025,
  # more settings
}


  • Provide default settings for the host name.
    [link]

    # config/environments/development.rb
config.action_mailer.default_url_options = { host: "#{local_ip}:3000" }

# config/environments/production.rb
config.action_mailer.default_url_options = { host: 'your_site.com' }

# in your mailer class
default_url_options[:host] = 'your_site.com'


  • If you need to use a link to your site in an email, always use the _url, not
    _path methods. The _url methods include the host name and the _path
    methods don’t.
    [link]

    # bad
You can always find more info about this course
<%= link_to 'here', course_path(@course) %>

# good
You can always find more info about this course
<%= link_to 'here', course_url(@course) %>


  • Format the from and to addresses properly. Use the following format:
    [link]

    # in your mailer class
default from: 'Your Name <info@your_site.com>'


  • Make sure that the e-mail delivery method for your test environment is set to
    test:
    [link]

    # config/environments/test.rb

config.action_mailer.delivery_method = :test


  • The delivery method for development and production should be smtp:
    [link]

    # config/environments/development.rb, config/environments/production.rb

config.action_mailer.delivery_method = :smtp


  • When sending html emails all styles should be inline, as some mail clients
    have problems with external styles. This however makes them harder to maintain
    and leads to code duplication. There are two similar gems that transform the
    styles and put them in the corresponding html tags:
    premailer-rails and
    roadie.
    [link]


  • Sending emails while generating page response should be avoided. It causes
    delays in loading of the page and request can timeout if multiple email are
    sent. To overcome this emails can be sent in background process with the help
    of sidekiq gem.
    [link]

Active Support Core Extensions


  • Prefer Ruby 2.3’s safe navigation operator &. over ActiveSupport#try!.
    [link]
# bad
obj.try! :fly

# good
obj&.fly

  • Prefer Ruby’s Standard Library methods over ActiveSupport aliases.
    [link]
# bad
'the day'.starts_with? 'th'
'the day'.ends_with? 'ay'

# good
'the day'.start_with? 'th'
'the day'.end_with? 'ay'

  • Prefer Ruby’s Standard Library over uncommon ActiveSupport extensions.
    [link]
# bad
(1..50).to_a.forty_two
1.in? [1, 2]
'day'.in? 'the day'

# good
(1..50).to_a[41]
[1, 2].include? 1
'the day'.include? 'day'

  • Prefer Ruby’s comparison operators over ActiveSupport’s Array#inquiry, and String#inquiry.
    [link]
# bad - String#inquiry
ruby = 'two'.inquiry
ruby.two?

# good
ruby = 'two'
ruby == 'two'

# bad - Array#inquiry
pets = %w(cat dog).inquiry
pets.gopher?

# good
pets = %w(cat dog)
pets.include? 'cat'

Time


  • Config your timezone accordingly in application.rb.
    [link]

    config.time_zone = 'Eastern European Time'
# optional - note it can be only :utc or :local (default is :utc)
config.active_record.default_timezone = :local


  • Don’t use Time.parse.
    [link]

    # bad
Time.parse('2015-03-02 19:05:37') # => Will assume time string given is in the system's time zone.

# good
Time.zone.parse('2015-03-02 19:05:37') # => Mon, 02 Mar 2015 19:05:37 EET +02:00


  • Don’t use String#to_time
    [link]

    # bad - assumes time string given is in the system's time zone.
'2015-03-02 19:05:37'.to_time

# good
Time.zone.parse('2015-03-02 19:05:37') # => Mon, 02 Mar 2015 19:05:37 EET +02:00


  • Don’t use Time.now.
    [link]

    # bad
Time.now # => Returns system time and ignores your configured time zone.

# good
Time.zone.now # => Fri, 12 Mar 2014 22:04:47 EET +02:00
Time.current # Same thing but shorter.

Bundler


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


  • 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.
    [link]


  • 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:
    [link]

    # 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.
    [link]

Managing processes


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

Further Reading

There are a few excellent resources on Rails style, that you should consider if
you have time to spare:

Contributing

Nothing written in this guide is set in stone. It’s my desire to work together
with everyone interested in Rails coding style, so that we could ultimately
create a resource that will be beneficial to the entire Ruby community.

Feel free to open tickets or send pull requests with improvements. Thanks in
advance for your help!

You can also support the project (and RuboCop) with financial contributions via
Patreon.

How to Contribute?

It’s easy, just follow the contribution guidelines.

License

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

Spread the Word

A community-driven style guide is of little use to a community that doesn’t know
about its existence. Tweet about the guide, share it with your friends and
colleagues. Every comment, suggestion or opinion we get makes the guide just a
little bit better. And we want to have the best possible guide, don’t we?

Cheers,

Bozhidar