Your Rails app needs custom configuration so you run off to GitHub to find a gem for that. Stop.

That would’ve been prudent in the bad ole’ days, but Rails 3 makes adding custom configuration dead simple. You don't have to shouldn’t add a dependency. Here’s how easy it is:

Easy Access

There are two ways to access our application’s configuration object in Rails 3.

MyApp::Application.config
# or
Rails.application.config

In my opinion, both of these are too verbose, so I add a convenience method to config/application.rb just inside my application’s top-level module:

module MyApp
  def self.config
    Application.config
  end
end

Now we have easy access to the configuration object:

MyApp.config

Right now that object is a bucket full of Rails configurations. How do we get our own settings in there?

Just add Yaml

Add a config.yml file to our app’s config directory. Put some settings in there.

site_name: "My Application"
contact_email: "email@myapp.com"

Copy the file to a new one called config.yml.example. Gitignore the real one. Check the example in to version control.

cp config/config.yml config/config.yml.example
echo "config/config.yml" >> .gitignore

Load it

We can add custom settings to Rails’ configuration manually like so:

module MyApp
  class Application < Rails::Application
    config.site_name = "My Application"
  end
end

But we want to load in all the settings from config.yml, so manual ain’t gonna cut it. Instead, load the Yaml file and send setter methods to the Application object for each setting, like so:

# inside MyApp::Application class
YAML.load_file("#{Rails.root}/config/config.yml").each { |k,v| config.send "#{k}=", v }

It’s as simple as that.

Go Crazy

This probably solves only the most basic of needs, but at just one LOC it is quite easy to extend ;). A few things that might be worth adding:

1. Environment separation
2. Shared settings
3. Nested settings

I’ll leave those as very easy exercises for the reader.