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:

  1. require "config/boot.rb" to set up load paths.

  2. require railties and engines.

  3. Define Rails.application as class MyApp::Application < Rails::Application.

  4. Run config.before_configuration callbacks.

  5. Load config/environments/ENV.rb.

  6. Run config.before_initialize callbacks.

  7. 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.

  8. Custom Railtie#initializers added by railties, engines, and applications are executed.

  9. Build the middleware stack and run to_prepare callbacks.

  10. Run config.before_eager_load and eager_load! if eager_load is true.

  11. Run config.after_initialize callbacks.

Namespace

Module

Class

Methods

Attributes

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

Class Public methods

create(initial_variable_values = {}, &block)

📝 Source code 
# File railties/lib/rails/application.rb, line 84
      def create(initial_variable_values = {}, &block)
        new(initial_variable_values, &block).run_load_hooks!
      end
🔎 See on GitHub

find_root(from)

📝 Source code 
# File railties/lib/rails/application.rb, line 88
      def find_root(from)
        find_root_with_flag "config.ru", from, Dir.pwd
      end
🔎 See on GitHub

inherited(base)

📝 Source code 
# File railties/lib/rails/application.rb, line 71
      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
🔎 See on GitHub

instance()

📝 Source code 
# File railties/lib/rails/application.rb, line 80
      def instance
        super.run_load_hooks!
      end
🔎 See on GitHub

new(initial_variable_values = {}, &block)

📝 Source code 
# File railties/lib/rails/application.rb, line 109
    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
🔎 See on GitHub

Instance Public 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 
# File railties/lib/rails/application.rb, line 288
    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
🔎 See on GitHub

console(&blk)

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

📝 Source code 
# File railties/lib/rails/application.rb, line 371
    def console(&blk)
      self.class.console(&blk)
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 492
    def credentials
      @credentials ||= encrypted(config.credentials.content_path, key_path: config.credentials.key_path)
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 244
    def deprecators
      @deprecators ||= ActiveSupport::Deprecation::Deprecators.new.tap do |deprecators|
        deprecators[:railties] = Rails.deprecator
      end
    end
🔎 See on GitHub

eager_load!()

Eager loads the application code.

📝 Source code 
# File railties/lib/rails/application.rb, line 550
    def eager_load!
      Rails.autoloaders.each(&:eager_load)
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 511
    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
🔎 See on GitHub

env_config()

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

📝 Source code 
# File railties/lib/rails/application.rb, line 317
    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
🔎 See on GitHub

generators(&blk)

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

📝 Source code 
# File railties/lib/rails/application.rb, line 377
    def generators(&blk)
      self.class.generators(&blk)
    end
🔎 See on GitHub

initialized?()

Returns true if the application is initialized.

📝 Source code 
# File railties/lib/rails/application.rb, line 134
    def initialized?
      @initialized
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 359
    def initializer(name, opts = {}, &block)
      self.class.initializer(name, opts, &block)
    end
🔎 See on GitHub

isolate_namespace(mod)

Sends the isolate_namespace method up to the class method.

📝 Source code 
# File railties/lib/rails/application.rb, line 388
    def isolate_namespace(mod)
      self.class.isolate_namespace(mod)
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 172
    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
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 236
    def message_verifier(verifier_name)
      message_verifiers[verifier_name]
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 208
    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
🔎 See on GitHub

name()

Returns the dasherized application name.

MyApp::Application.new.name => "my-app"
📝 Source code 
# File railties/lib/rails/application.rb, line 141
    def name
      self.class.name.underscore.dasherize.delete_suffix("/application")
    end
🔎 See on GitHub

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 
# File railties/lib/rails/application.rb, line 352
    def rake_tasks(&block)
      self.class.rake_tasks(&block)
    end
🔎 See on GitHub

reload_routes!()

Reload application routes regardless if they changed or not.

📝 Source code 
# File railties/lib/rails/application.rb, line 160
    def reload_routes!
      routes_reloader.reload!
    end
🔎 See on GitHub

runner(&blk)

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

📝 Source code 
# File railties/lib/rails/application.rb, line 365
    def runner(&blk)
      self.class.runner(&blk)
    end
🔎 See on GitHub

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.

In development and test, this is randomly generated and stored in a temporary file in tmp/local_secret.txt.

You can also set ENV["SECRET_KEY_BASE_DUMMY"] to trigger the use of a randomly generated secret_key_base that’s stored in a temporary file. 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.

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

📝 Source code 
# File railties/lib/rails/application.rb, line 474
    def secret_key_base
      config.secret_key_base
    end
🔎 See on GitHub

server(&blk)

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

📝 Source code 
# File railties/lib/rails/application.rb, line 383
    def server(&blk)
      self.class.server(&blk)
    end
🔎 See on GitHub

Instance Protected methods

ensure_generator_templates_added()

📝 Source code 
# File railties/lib/rails/application.rb, line 628
    def ensure_generator_templates_added
      configured_paths = config.generators.templates
      configured_paths.unshift(*(paths["lib/templates"].existent - configured_paths))
    end
🔎 See on GitHub