Config file in Ruby on Rails

There are a bunch of config files in a Ruby on Rails app. The most popular ist the “database.yml” config file. This is for configuring the database connection in 3 different environments.

Assume you want to have your config file, in the same style as the database.yml file. Where you can configure some program logic depending on the environment. Let’s call this config file “config.yml” and place it under the “config/” directory.

There are now different ways to access the values from the file. I prefer to use this code:

class Settings
 raw_config = File.read("#{::Rails.root.to_s}/config/config.yml")
 erb_config = ERB.new(raw_config).result
 settings = YAML.load(erb_config)[::Rails.env]

 if settings
   settings.each { |name, value|
     instance_variable_set("@#{name}", value)
     self.class.class_eval { attr_reader name.intern }
   }
 end
end

Just place it into the “environment.rb” file. My environment.rb file looks like that:

# Load the rails application
require File.expand_path('../application', __FILE__)

class Settings
 raw_config = File.read("#{::Rails.root.to_s}/config/config.yml")
 erb_config = ERB.new(raw_config).result
 settings = YAML.load(erb_config)[::Rails.env]

 if settings
   settings.each { |name, value|
     instance_variable_set("@#{name}", value)
     self.class.class_eval { attr_reader name.intern }
   }
 end
end

# Initialize the rails application
TrophicWeb::Application.initialize!

Before the initialization of the app the Settings class will read all the key value pairs from the config.yml file. All values are accessible via variable calls. If your config.yml file looks like this:

development:
   neo4j_service: http://localhost:7474/db/data/cypher
test:
   neo4j_service: http://localhost:7474/db/data/cypher
production:
   neo4j_service: http://ec2-bimbo.aws.com:7474/db/data/cypher

Than you can access the values like this:

  Settings.neo4j_service

That’s it.