Easy-peasy external settings for your Rails app.

# Gemfile
gem 'choices'

In your app initializer block:

config.from_file 'settings.yml'

This will read configuration from "config/settings.yml" and, additionally, "settings.local.yml" if it exists. You should check the main file into version control, but not the ".local" file which is to be used for per-machine configuration: tweaks in development or private keys in production, for example.

# .gitignore
config/settings.local.yml

Configuration files can contain ERB; this is useful for reading in dynamic config such as from environment variables:

# settings.yml
defaults: &defaults
  secret_token: <%= ENV['COOKIE_SECRET'] %>
  heroku: <%= !!ENV['HEROKU_TYPE'] %>
  mongodb:
    uri: <%= ENV['MONGOHQ_URL'] %>

development:
  <<: *defaults

test: &testing
  <<: *defaults
  secret_token: <%= "banana" * 5 %>
  mongodb:
    database: myapp_test

cucumber:
  <<: *testing

The ".local" file can contain overrides for your development environment:

# settings.local.yml
development:
  mongodb:
    database: myapp_dev

Finally, the config keys can be read in your app as such:

Rails.configuration.heroku              #=> false
Rails.configuration.mongodb.database    #=> "myapp_dev"