The Configuration class holds all the parameters for the Initializer and ships with defaults that suites most Rails applications. But it’s possible to overwrite everything. Usually, you’ll create an Configuration file implicitly through the block running on the Initializer, but it’s also possible to create the Configuration instance in advance and pass it in like this:

config = Rails::Configuration.new
Rails::Initializer.run(:process, config)
Methods
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B
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Attributes
[RW] action_controller

A stub for setting options on ActionController::Base
[RW] action_mailer

A stub for setting options on ActionMailer::Base
[RW] action_view

A stub for setting options on ActionView::Base
[RW] action_web_service

A stub for setting options on ActionWebService::Base
[RW] active_record

A stub for setting options on ActiveRecord::Base
[RW] breakpoint_server

Whether or not to use the breakpoint server (boolean)
[RW] cache_classes

Whether or not classes should be cached (set to false if you want application classes to be reloaded on each request)
[RW] connection_adapters

The list of connection adapters to load. (By default, all connection adapters are loaded. You can set this to be just the adapter(s) you will use to reduce your application’s load time.)
[RW] controller_paths

The list of paths that should be searched for controllers. (Defaults to app/controllers and components.)
[RW] database_configuration_file

The path to the database configuration file to use. (Defaults to config/database.yml.)
[RW] frameworks

The list of rails framework components that should be loaded. (Defaults to :active_record, :action_controller, :action_view, :action_mailer, and :action_web_service).
[RW] load_once_paths

An array of paths from which Rails will automatically load from only once. All elements of this array must also be in load_paths.
[RW] load_paths

An array of additional paths to prepend to the load path. By default, all app, lib, vendor and mock paths are included in this list.
[RW] log_level

The log level to use for the default Rails logger. In production mode, this defaults to :info. In development mode, it defaults to :debug.
[RW] log_path

The path to the log file to use. Defaults to log/#{environment}.log (e.g. log/development.log or log/production.log).
[RW] logger

The specific logger to use. By default, a logger will be created and initialized using log_path and log_level, but a programmer may specifically set the logger to use via this accessor and it will be used directly.
[RW] plugin_paths

The path to the root of the plugins directory. By default, it is in vendor/plugins.
[RW] plugins

The list of plugins to load. If this is set to nil, all plugins will be loaded. If this is set to [], no plugins will be loaded. Otherwise, plugins will be loaded in the order specified.
[R] root_path

The application’s base directory.
[RW] view_path

The root of the application’s views. (Defaults to app/views.)
[RW] whiny_nils

Set to true if you want to be warned (noisily) when you try to invoke any method of nil. Set to false for the standard Ruby behavior.
Class Public methods
new()

Create a new Configuration instance, initialized with the default values.

Source: show 

# File rails/railties/lib/initializer.rb, line 508
def initialize
  set_root_path!

  self.frameworks                   = default_frameworks
  self.load_paths                   = default_load_paths
  self.load_once_paths              = default_load_once_paths
  self.log_path                     = default_log_path
  self.log_level                    = default_log_level
  self.view_path                    = default_view_path
  self.controller_paths             = default_controller_paths
  self.cache_classes                = default_cache_classes
  self.breakpoint_server            = default_breakpoint_server
  self.whiny_nils                   = default_whiny_nils
  self.plugins                      = default_plugins
  self.plugin_paths                 = default_plugin_paths
  self.database_configuration_file  = default_database_configuration_file

  for framework in default_frameworks
    self.send("#{framework}=", Rails::OrderedOptions.new)
  end
end
Instance Public methods
after_initialize(&after_initialize_block)

Sets a block which will be executed after rails has been fully initialized. Useful for per-environment configuration which depends on the framework being fully initialized.

Source: show 

# File rails/railties/lib/initializer.rb, line 569
def after_initialize(&after_initialize_block)
  @after_initialize_block = after_initialize_block
end
after_initialize_block()

Returns the block set in #after_initialize

Source: show 

# File rails/railties/lib/initializer.rb, line 574
def after_initialize_block
  @after_initialize_block
end
builtin_directories()

Source: show 

# File rails/railties/lib/initializer.rb, line 587
def builtin_directories
  # Include builtins only in the development environment.
  (environment == 'development') ? Dir["#{RAILTIES_PATH}/builtin/*/"] : []
end
database_configuration()

Loads and returns the contents of the database_configuration_file. The contents of the file are processed via ERB before being sent through YAML::load.

Source: show 

# File rails/railties/lib/initializer.rb, line 550
def database_configuration
  YAML::load(ERB.new(IO.read(database_configuration_file)).result)
end
environment()

Return the currently selected environment. By default, it returns the value of the RAILS_ENV constant.

Source: show 

# File rails/railties/lib/initializer.rb, line 562
def environment
  ::RAILS_ENV
end
environment_path()

The path to the current environment’s file (development.rb, etc.). By default the file is at config/environments/#{environment}.rb.

Source: show 

# File rails/railties/lib/initializer.rb, line 556
def environment_path
  "#{root_path}/config/environments/#{environment}.rb"
end
framework_paths()

Source: show 

# File rails/railties/lib/initializer.rb, line 592
def framework_paths
  # TODO: Don't include dirs for frameworks that are not used
  %w(
    railties
    railties/lib
    actionpack/lib
    activesupport/lib
    activerecord/lib
    actionmailer/lib
    actionwebservice/lib
  ).map { |dir| "#{framework_root_path}/#{dir}" }.select { |dir| File.directory?(dir) }
end
set_root_path!()

Set the #root_path to RAILS_ROOT and canonicalize it.

Source: show 

# File rails/railties/lib/initializer.rb, line 531
def set_root_path!
  raise 'RAILS_ROOT is not set' unless defined?(::RAILS_ROOT)
  raise 'RAILS_ROOT is not a directory' unless File.directory?(::RAILS_ROOT)

  @root_path =
    # Pathname is incompatible with Windows, but Windows doesn't have
    # real symlinks so File.expand_path is safe.
    if RUBY_PLATFORM =~ %r(:?mswin|mingw)/
      File.expand_path(::RAILS_ROOT)

    # Otherwise use Pathname#realpath which respects symlinks.
    else
      Pathname.new(::RAILS_ROOT).realpath.to_s
    end
end
to_prepare(&callback)

Add a preparation callback that will run before every request in development mode, or before the first request in production.

See Dispatcher#to_prepare.

Source: show 

# File rails/railties/lib/initializer.rb, line 582
def to_prepare(&callback)
  require 'dispatcher' unless defined?(::Dispatcher)
  Dispatcher.to_prepare(&callback)
end