class `Rails::Application`

An Engine with the responsibility of coordinating the whole boot process.

Initialization

Rails::Application is responsible for executing all railties and engines initializers. It also executes some bootstrap initializers (check Rails::Application::Bootstrap) and finishing initializers, after all the others are executed (check Rails::Application::Finisher).

Configuration

Besides providing the same configuration as Rails::Engine and Rails::Railtie, the application object has several specific configurations, for example enable_reloading, consider_all_requests_local, filter_parameters, logger, and so forth.

Check Rails::Application::Configuration to see them all.

Routes

The application object is also responsible for holding the routes and reloading routes whenever the files change in development.

Middlewares

The Application is also responsible for building the middleware stack.

Booting process

The application is also responsible for setting up and executing the booting process. From the moment you require config/application.rb in your app, the booting process goes like this:

require "config/boot.rb" to set up load paths.
require railties and engines.
Define Rails.application as class MyApp::Application < Rails::Application.
Run config.before_configuration callbacks.
Load config/environments/ENV.rb.
Run config.before_initialize callbacks.
Run Railtie#initializer defined by railties, engines, and application. One by one, each engine sets up its load paths and routes, and runs its config/initializers/* files.
Custom Railtie#initializers added by railties, engines, and applications are executed.
Build the middleware stack and run to_prepare callbacks.
Run config.before_eager_load and eager_load! if eager_load is true.
Run config.after_initialize callbacks.

Inherits From

class Engine

Attributes

[RW]	`assets`
[R]	`autoloaders`
[W]	`config`
[W]	`credentials`
[R]	`executor`
[R]	`reloader`
[R]	`reloaders`
[RW]	`sandbox`
[RW]	`sandbox?`

Public class methods

`create(initial_variable_values = {}, &block)`

Source code GitHub

# File railties/lib/rails/application.rb, line 82
def create(initial_variable_values = {}, &block)
  new(initial_variable_values, &block).run_load_hooks!
end

`find_root(from)`

Source code GitHub

# File railties/lib/rails/application.rb, line 86
def find_root(from)
  find_root_with_flag "config.ru", from, Dir.pwd
end

`inherited(base)`

Source code GitHub

# File railties/lib/rails/application.rb, line 69
def inherited(base)
  super
  Rails.app_class = base
  # lib has to be added to $LOAD_PATH unconditionally, even if it's in the
  # autoload paths and config.add_autoload_paths_to_load_path is false.
  add_lib_to_load_path!(find_root(base.called_from))
  ActiveSupport.run_load_hooks(:before_configuration, base)
end

`instance()`

Source code GitHub

# File railties/lib/rails/application.rb, line 78
def instance
  super.run_load_hooks!
end

`new(initial_variable_values = {}, &block)`

Source code GitHub

# File railties/lib/rails/application.rb, line 107
def initialize(initial_variable_values = {}, &block)
  super()
  @initialized       = false
  @reloaders         = []
  @routes_reloader   = nil
  @app_env_config    = nil
  @ordered_railties  = nil
  @railties          = nil
  @key_generators    = {}
  @message_verifiers = nil
  @deprecators       = nil
  @ran_load_hooks    = false

  @executor          = Class.new(ActiveSupport::Executor)
  @reloader          = Class.new(ActiveSupport::Reloader)
  @reloader.executor = @executor

  @autoloaders = Rails::Autoloaders.new

  # are these actually used?
  @initial_variable_values = initial_variable_values
  @block = block
end

Public instance methods

`config_for(name, env: Rails.env)`

Convenience for loading config/foo.yml for the current Rails env. Example:

# config/exception_notification.yml:
production:
  url: http://127.0.0.1:8080
  namespace: my_app_production

development:
  url: http://localhost:3001
  namespace: my_app_development

# config/environments/production.rb
Rails.application.configure do
  config.middleware.use ExceptionNotifier, config_for(:exception_notification)
end

You can also store configurations in a shared section which will be merged with the environment configuration

# config/example.yml
shared:
  foo:
    bar:
      baz: 1

development:
  foo:
    bar:
      qux: 2

# development environment
Rails.application.config_for(:example)[:foo][:bar]
# => { baz: 1, qux: 2 }

Source code GitHub

# File railties/lib/rails/application.rb, line 290
def config_for(name, env: Rails.env)
  yaml = name.is_a?(Pathname) ? name : Pathname.new("#{paths["config"].existent.first}/#{name}.yml")

  if yaml.exist?
    require "erb"
    all_configs    = ActiveSupport::ConfigurationFile.parse(yaml).deep_symbolize_keys
    config, shared = all_configs[env.to_sym], all_configs[:shared]

    if shared
      config = {} if config.nil? && shared.is_a?(Hash)
      if config.is_a?(Hash) && shared.is_a?(Hash)
        config = shared.deep_merge(config)
      elsif config.nil?
        config = shared
      end
    end

    if config.is_a?(Hash)
      config = ActiveSupport::OrderedOptions.new.update(config)
    end

    config
  else
    raise "Could not load configuration. No such file - #{yaml}"
  end
end

`console(&blk)`

Sends any console called in the instance of a new application up to the console method defined in Rails::Railtie.

Source code GitHub

# File railties/lib/rails/application.rb, line 373
def console(&blk)
  self.class.console(&blk)
end

`credentials()`

Returns an ActiveSupport::EncryptedConfiguration instance for the credentials file specified by config.credentials.content_path.

By default, config.credentials.content_path will point to either config/credentials/#{environment}.yml.enc for the current environment (for example, config/credentials/production.yml.enc for the production environment), or config/credentials.yml.enc if that file does not exist.

The encryption key is taken from either ENV["RAILS_MASTER_KEY"], or from the file specified by config.credentials.key_path. By default, config.credentials.key_path will point to either config/credentials/#{environment}.key for the current environment, or config/master.key if that file does not exist.

Source code GitHub

# File railties/lib/rails/application.rb, line 497
def credentials
  @credentials ||= encrypted(config.credentials.content_path, key_path: config.credentials.key_path)
end

`deprecators()`

A managed collection of deprecators (ActiveSupport::Deprecation::Deprecators). The collection’s configuration methods affect all deprecators in the collection. Additionally, the collection’s silence method silences all deprecators in the collection for the duration of a given block.

Source code GitHub

# File railties/lib/rails/application.rb, line 246
def deprecators
  @deprecators ||= ActiveSupport::Deprecation::Deprecators.new.tap do |deprecators|
    deprecators[:railties] = Rails.deprecator
  end
end

`eager_load!()`

Eager loads the application code.

Source code GitHub

# File railties/lib/rails/application.rb, line 555
def eager_load!
  Rails.autoloaders.each(&:eager_load)
end

`encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")`

Returns an ActiveSupport::EncryptedConfiguration instance for an encrypted file. By default, the encryption key is taken from either ENV["RAILS_MASTER_KEY"], or from the config/master.key file.

my_config = Rails.application.encrypted("config/my_config.enc")

my_config.read
# => "foo:\n  bar: 123\n"

my_config.foo.bar
# => 123

Encrypted files can be edited with the bin/rails encrypted:edit command. (See the output of bin/rails encrypted:edit --help for more information.)

Source code GitHub

# File railties/lib/rails/application.rb, line 516
def encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")
  ActiveSupport::EncryptedConfiguration.new(
    config_path: Rails.root.join(path),
    key_path: Rails.root.join(key_path),
    env_key: env_key,
    raise_if_missing_key: config.require_master_key
  )
end

`env_config()`

Stores some of the Rails initial environment parameters which will be used by middlewares and engines to configure themselves.

Source code GitHub

# File railties/lib/rails/application.rb, line 319
def env_config
  @app_env_config ||= super.merge(
      "action_dispatch.parameter_filter" => filter_parameters,
      "action_dispatch.redirect_filter" => config.filter_redirect,
      "action_dispatch.secret_key_base" => secret_key_base,
      "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions,
      "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local,
      "action_dispatch.log_rescued_responses" => config.action_dispatch.log_rescued_responses,
      "action_dispatch.debug_exception_log_level" => ActiveSupport::Logger.const_get(config.action_dispatch.debug_exception_log_level.to_s.upcase),
      "action_dispatch.logger" => Rails.logger,
      "action_dispatch.backtrace_cleaner" => Rails.backtrace_cleaner,
      "action_dispatch.key_generator" => key_generator,
      "action_dispatch.http_auth_salt" => config.action_dispatch.http_auth_salt,
      "action_dispatch.signed_cookie_salt" => config.action_dispatch.signed_cookie_salt,
      "action_dispatch.encrypted_cookie_salt" => config.action_dispatch.encrypted_cookie_salt,
      "action_dispatch.encrypted_signed_cookie_salt" => config.action_dispatch.encrypted_signed_cookie_salt,
      "action_dispatch.authenticated_encrypted_cookie_salt" => config.action_dispatch.authenticated_encrypted_cookie_salt,
      "action_dispatch.use_authenticated_cookie_encryption" => config.action_dispatch.use_authenticated_cookie_encryption,
      "action_dispatch.encrypted_cookie_cipher" => config.action_dispatch.encrypted_cookie_cipher,
      "action_dispatch.signed_cookie_digest" => config.action_dispatch.signed_cookie_digest,
      "action_dispatch.cookies_serializer" => config.action_dispatch.cookies_serializer,
      "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest,
      "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations,
      "action_dispatch.cookies_same_site_protection" => coerce_same_site_protection(config.action_dispatch.cookies_same_site_protection),
      "action_dispatch.use_cookies_with_metadata" => config.action_dispatch.use_cookies_with_metadata,
      "action_dispatch.content_security_policy" => config.content_security_policy,
      "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only,
      "action_dispatch.content_security_policy_nonce_generator" => config.content_security_policy_nonce_generator,
      "action_dispatch.content_security_policy_nonce_directives" => config.content_security_policy_nonce_directives,
      "action_dispatch.permissions_policy" => config.permissions_policy,
    )
end

`generators(&blk)`

Sends any generators called in the instance of a new application up to the generators method defined in Rails::Railtie.

Source code GitHub

# File railties/lib/rails/application.rb, line 379
def generators(&blk)
  self.class.generators(&blk)
end

`initialized?()`

Returns true if the application is initialized.

Source code GitHub

# File railties/lib/rails/application.rb, line 132
def initialized?
  @initialized
end

`initializer(name, opts = {}, &block)`

Sends the initializers to the initializer method defined in the Rails::Initializable module. Each Rails::Application class has its own set of initializers, as defined by the Initializable module.

Source code GitHub

# File railties/lib/rails/application.rb, line 361
def initializer(name, opts = {}, &block)
  self.class.initializer(name, opts, &block)
end

`isolate_namespace(mod)`

Sends the isolate_namespace method up to the class method.

Source code GitHub

# File railties/lib/rails/application.rb, line 390
def isolate_namespace(mod)
  self.class.isolate_namespace(mod)
end

`key_generator(secret_key_base = self.secret_key_base)`

Returns a key generator (ActiveSupport::CachingKeyGenerator) for a specified secret_key_base. The return value is memoized, so additional calls with the same secret_key_base will return the same key generator instance.

Source code GitHub

# File railties/lib/rails/application.rb, line 174
def key_generator(secret_key_base = self.secret_key_base)
  # number of iterations selected based on consultation with the google security
  # team. Details at https://github.com/rails/rails/pull/6952#issuecomment-7661220
  @key_generators[secret_key_base] ||= ActiveSupport::CachingKeyGenerator.new(
    ActiveSupport::KeyGenerator.new(secret_key_base, iterations: 1000)
  )
end

`message_verifier(verifier_name)`

Returns a message verifier object.

This verifier can be used to generate and verify signed messages in the application.

It is recommended not to use the same verifier for different things, so you can get different verifiers passing the verifier_name argument.

For instance, ActiveStorage::Blob.signed_id_verifier is implemented using this feature, which assures that the IDs strings haven’t been tampered with and are safe to use in a finder.

See the ActiveSupport::MessageVerifier documentation for more information.

Parameters

verifier_name - the name of the message verifier.

Examples

message = Rails.application.message_verifier('my_purpose').generate('data to sign against tampering')
Rails.application.message_verifier('my_purpose').verify(message)
# => 'data to sign against tampering'

Source code GitHub

# File railties/lib/rails/application.rb, line 238
def message_verifier(verifier_name)
  message_verifiers[verifier_name]
end

`message_verifiers()`

Returns a message verifier factory (ActiveSupport::MessageVerifiers). This factory can be used as a central point to configure and create message verifiers (ActiveSupport::MessageVerifier) for your application.

By default, message verifiers created by this factory will generate messages using the default ActiveSupport::MessageVerifier options. You can override these options with a combination of ActiveSupport::MessageVerifiers#clear_rotations and ActiveSupport::MessageVerifiers#rotate. However, this must be done prior to building any message verifier instances. For example, in a before_initialize block:

# Use `url_safe: true` when generating messages
config.before_initialize do |app|
  app.message_verifiers.clear_rotations
  app.message_verifiers.rotate(url_safe: true)
end

Message verifiers created by this factory will always use a secret derived from secret_key_base when generating messages. clear_rotations will not affect this behavior. However, older secret_key_base values can be rotated for verifying messages:

# Fall back to old `secret_key_base` when verifying messages
config.before_initialize do |app|
  app.message_verifiers.rotate(secret_key_base: "old secret_key_base")
end

Source code GitHub

# File railties/lib/rails/application.rb, line 210
def message_verifiers
  @message_verifiers ||=
    ActiveSupport::MessageVerifiers.new do |salt, secret_key_base: self.secret_key_base|
      key_generator(secret_key_base).generate_key(salt)
    end.rotate_defaults
end

`name()`

Returns the dasherized application name.

MyApp::Application.new.name => "my-app"

Source code GitHub

# File railties/lib/rails/application.rb, line 139
def name
  self.class.name.underscore.dasherize.delete_suffix("/application")
end

`rake_tasks(&block)`

If you try to define a set of Rake tasks on the instance, these will get passed up to the Rake tasks defined on the application’s class.

Source code GitHub

# File railties/lib/rails/application.rb, line 354
def rake_tasks(&block)
  self.class.rake_tasks(&block)
end

`reload_routes!()`

Reload application routes regardless if they changed or not.

Source code GitHub

# File railties/lib/rails/application.rb, line 158
def reload_routes!
  if routes_reloader.execute_unless_loaded
    routes_reloader.loaded = false
  else
    routes_reloader.reload!
  end
end

`runner(&blk)`

Sends any runner called in the instance of a new application up to the runner method defined in Rails::Railtie.

Source code GitHub

# File railties/lib/rails/application.rb, line 367
def runner(&blk)
  self.class.runner(&blk)
end

`secret_key_base()`

The secret_key_base is used as the input secret to the application’s key generator, which in turn is used to create all ActiveSupport::MessageVerifier and ActiveSupport::MessageEncryptor instances, including the ones that sign and encrypt cookies.

We look for it first in ENV["SECRET_KEY_BASE"], then in credentials.secret_key_base. For most applications, the correct place to store it is in the encrypted credentials file.

In development and test, if the secret_key_base is still empty, it is randomly generated and stored in a temporary file in tmp/local_secret.txt.

Generating a random secret_key_base and storing it in tmp/local_secret.txt can also be triggered by setting ENV["SECRET_KEY_BASE_DUMMY"]. This is useful when precompiling assets for production as part of a build step that otherwise does not need access to the production secrets.

Dockerfile example: RUN SECRET_KEY_BASE_DUMMY=1 bundle exec rails assets:precompile.

Source code GitHub

# File railties/lib/rails/application.rb, line 479
def secret_key_base
  config.secret_key_base
end

`server(&blk)`

Sends any server called in the instance of a new application up to the server method defined in Rails::Railtie.

Source code GitHub

# File railties/lib/rails/application.rb, line 385
def server(&blk)
  self.class.server(&blk)
end

Protected instance methods

`ensure_generator_templates_added()`

Source code GitHub

# File railties/lib/rails/application.rb, line 633
def ensure_generator_templates_added
  configured_paths = config.generators.templates
  configured_paths.unshift(*(paths["lib/templates"].existent - configured_paths))
end

class Rails::Application

Initialization

Configuration

Routes

Middlewares

Booting process

Inherits From

Attributes

Public class methods

create(initial_variable_values = {}, &block)

find_root(from)

inherited(base)

instance()

new(initial_variable_values = {}, &block)

Public instance methods

config_for(name, env: Rails.env)

console(&blk)

credentials()

deprecators()

eager_load!()

encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")

env_config()

generators(&blk)

initialized?()

initializer(name, opts = {}, &block)

isolate_namespace(mod)

key_generator(secret_key_base = self.secret_key_base)

message_verifier(verifier_name)

Parameters

Examples

message_verifiers()

name()

rake_tasks(&block)

reload_routes!()

runner(&blk)

secret_key_base()

server(&blk)

Protected instance methods

ensure_generator_templates_added()

Namespace

Definition files

class `Rails::Application`

`create(initial_variable_values = {}, &block)`

`find_root(from)`

`inherited(base)`

`instance()`

`new(initial_variable_values = {}, &block)`

`config_for(name, env: Rails.env)`

`console(&blk)`

`credentials()`

`deprecators()`

`eager_load!()`

`encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")`

`env_config()`

`generators(&blk)`

`initialized?()`

`initializer(name, opts = {}, &block)`

`isolate_namespace(mod)`

`key_generator(secret_key_base = self.secret_key_base)`

`message_verifier(verifier_name)`

`message_verifiers()`

`name()`

`rake_tasks(&block)`

`reload_routes!()`

`runner(&blk)`

`secret_key_base()`

`server(&blk)`

`ensure_generator_templates_added()`