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Easiest way to add multi-environment yaml settings to Rails, Sinatra, Pandrino and other ruby projects.
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Latest commit 0bb41e0 @fredwu fredwu Merge pull request #129 from irfanfadilah/master
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Config helps you easily manage environment specific settings in an easy and usable manner.


  • simple YAML config files
  • config files support ERB
  • config files support inheritance and multiple environments
  • access config information via convenient object member notation
  • support for multi-level settings (
  • local developer settings ignored when committing the code


  • Ruby 2.x
  • Rails >= 3.1 and 4
  • Padrino
  • Sinatra

For older versions of Rails or Ruby use AppConfig.


Installing on Rails 3 or 4

Add gem 'config' to your Gemfile and run bundle install to install it. Then run

rails g config:install

which will generate customizable config file config/initializers/config.rb and set of default settings files:


You can now edit them to adjust to your needs.

If you want to use Settings before rails application initialization process you can load Config railtie manually:

module Appname
  class Application < Rails::Application


    # ...

    config.time_zone = Settings.time_zone

    # ...


Installing on Padrino

Add the gem to your Gemfile and run bundle install to install it. Then edit app.rb and register Config

register Config

Installing on Sinatra

Add the gem to your Gemfile and run bundle install to install it. Afterwards in need to register Config in your app and give it a root so it can find the config files.

set :root, File.dirname(__FILE__)
register Config

It's also possible to initialize Config manually within your configure block if you want to just give it some yml paths to load from.

Config.load_and_set_settings("/path/to/yaml1", "/path/to/yaml2", ...)

Accessing the Settings object

After installing the gem, Settings object will become available globally and by default will be compiled from the files listed below. Settings defined in files that are lower in the list override settings higher.



Entries can be accessed via object member notation:


Nested entries are supported:


Alternatively, you can also use the [] operator if you don't know which exact setting you need to access ahead of time.

# All the following are equivalent to Settings.my_section.some_entry

Reloading settings

You can reload the Settings object at any time by running Settings.reload!.

Reloading settings and config files

You can also reload the Settings object from different config files at runtime.

For example, in your tests if you want to test the production settings, you can:

Rails.env = "production"
  Rails.root.join("config", "settings.yml").to_s,
  Rails.root.join("config", "settings", "#{Rails.env}.yml").to_s,
  Rails.root.join("config", "environments", "#{Rails.env}.yml").to_s

Environment specific config files

You can have environment specific config files. Environment specific config entries take precedence over common config entries.

Example development environment config file:


Example production environment config file:


Developer specific config files

If you want to have local settings, specific to your machine or development environment, you can use the following files, which are automatically .gitignore :

Rails.root.join("config", "settings.local.yml").to_s,
Rails.root.join("config", "settings", "#{Rails.env}.local.yml").to_s,
Rails.root.join("config", "environments", "#{Rails.env}.local.yml").to_s

Adding sources at runtime

You can add new YAML config files at runtime. Just use:


This will use the given source.yml file and use its settings to overwrite any previous ones.

On the other hand, you can prepend a YML file to the list of configuration files:


This will do the same as add_source, but the given YML file will be loaded first (instead of last) and its settings will be overwritten by any other configuration file. This is especially useful if you want to define defaults.

One thing I like to do for my Rails projects is provide a local.yml config file that is .gitignored (so its independent per developer). Then I create a new initializer in config/initializers/add_local_config.rb with the contents


Note: this is an example usage, it is easier to just use the default local files settings.local.yml, settings/#{Rails.env}.local.yml and environments/#{Rails.env}.local.yml for your developer specific settings.

Embedded Ruby (ERB)

Embedded Ruby is allowed in the configuration files. Consider the two following config files.

  • #{Rails.root}/config/settings.yml
size: 1
  • #{Rails.root}/config/environments/development.yml
size: 2
computed: <%= 1 + 2 + 3 %>
  size: 3
  servers: [ {name:}, {name:} ]

Notice that the environment specific config entries overwrite the common entries.

Settings.size   # => 2
Settings.server # =>

Notice the embedded Ruby.

Settings.computed # => 6

Notice that object member notation is maintained even in nested entries.

Settings.section.size # => 3

Notice array notation and object member notation is maintained.

Settings.section.servers[0].name # =>
Settings.section.servers[1].name # =>


You can customize Config only once, preferably during application initialization phase:

Config.setup do |config|
  config.const_name = 'Settings'
  config.knockout_prefix = nil

After installing Config in Rails, you will find this configuration at config/initializers/config.rb.

Following options are available:

  • const_name - name of the object holing you settings. Default: 'Settings'

Inheritance customization (check Deep Merge for more details):

  • knockout_prefix - ability to remove elements of the array set in earlier loaded settings file. Default: nil

Working with Heroku

Heroku uses ENV object to store sensitive settings which are like the local files described above. You cannot upload such files to Heroku because it's ephemeral filesystem gets recreated from the git sources on each instance refresh.

To use config with Heroku just set the use_env var to true in your config/initializers/config.rb file. Eg:

Config.setup do |config|
  config.const_name = 'AppSettings'
  config.use_env = true

Now config would read values from the ENV object to the settings. For the example above it would look for keys starting with 'AppSettings'. Eg:

ENV['AppSettings.section.size'] = 1
ENV['AppSettings.section.server'] = ''

It won't work with arrays, though.

To upload your local values to Heroku you could ran bundle exec rake config:heroku.



$ appraisal install

Running the test suite

$ appraisal rspec



Config is released under the MIT License.

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