Rails: Using custom config files with the config_for method

You can use the config.x Show archive.org snapshot configuration in combination with config_for to configure global settings for your Rails 4.2+ application.

Example

In your config/application.rb assign the settings from e.g. config/settings.yml as follows:

Copymodule FooApplication
  class Application < Rails::Application
    config.x.settings = config_for(:settings)
  end
end

The config/settings.yml might look as follows:

Copyshared: &shared
  email: info@example.com
  google_analytics:
    container: UA-123456-12
    
test:
  <<: *shared
  
development:
  <<: *shared    

production:
  <<: *shared
  email: production@example.com    

Keys under the shared namespace are shared between all environments. Environment specific configs will override those shared values. Afterwards you can access these settings with e.g. Rails.application.config.x.settings.google_analytics.fetch(:container) or Rails.configuration.x.settings.google_analytics.fetch(:container) in your application.

Additional notes

• The config.x is a dedicated namespace and helps you to avoid collisions with config options related to Rails itself.

• The config.x returns an OrderedOptions Show archive.org snapshot object for the first two levels, but not deeper.

• This approach might be preferred over global constants like config/constants/settings.rb:

  • It can be used in the Rails Configuration itself and all initializers.
  • It allows to write environment dependent settings.

• Undefined keys return nil if not present e.g. Rails.application.config.foobar => nil.

• If you need to ensure the value of key is not blank, use the bang method e.g. Rails.application.config.foobar!. This is recommended for a value that must exist in any case (no blank value).

• For many other cases it more useful to use #fetch instead of the attribute accessors to ensure you have no typos in your config e.g. Rails.application.config.fetch(:foobar). You might also want to chain the method calls for nested configs e.g. Rails.application.config.fetch(:foobar).fetch(:bar). This approach allows you to have '', true, false and nil in your config.