November 10, 2009

Posted by John

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Config So Simple Your Mama Could Use It

Tonight, Kastner asked me if I had anything to do some simple configuration for something he was working on. I’ve got a simple module and yaml file that I’ve been using so I gist’d it. It then occurred to me that I might as well share it here too.

The Yaml

Below is an example of the yaml file. Basically, I setup some defaults and then customize each environment as needed.

DEFAULTS: &DEFAULTS
  email: no-reply@harmonyapp.com
  email_signature: |
    Regards,
    The Harmony Team
 
development:
  domain: harmonyapp.local
  <<: *DEFAULTS
  
test:
  domain: harmonyapp.com
  <<: *DEFAULTS
 
production:
  domain: harmonyapp.com
  <<: *DEFAULTS

The Module

The module can read and write to the config and even loads the Yaml file the first time you try to read a configuration key.

module Harmony
  # Allows accessing config variables from harmony.yml like so:
  # Harmony[:domain] => harmonyapp.com
  def self.[](key)
    unless @config
      raw_config = File.read(RAILS_ROOT + "/config/harmony.yml")
      @config = YAML.load(raw_config)[RAILS_ENV].symbolize_keys
    end
    @config[key]
  end
  
  def self.[]=(key, value)
    @config[key.to_sym] = value
  end
end

If I wanted to get the domain, I would do the following:

Harmony[:domain]

Nothing fancy, but it gets the job done. I just drop the yaml file in config/ and the module in lib/. Obviously, you would rename the module and yaml file to whatever constant you want, such as App or something related to your application’s name. I know there are gems and plugins to do configuration, but when something this simple gets the job done, I figure why bother.

What do you all use for app configuration? What do you like about what you use?

10 Comments

Angel N. Sciortino

Nov 10, 2009

I have a very similar setup, except it checks for a local config file, which would be ignored in git. If it doesn’t exist, it loads the default config.


if File.exist?(RAILS_ROOT + "/config/config.local.yml")
  raw_config = File.read(RAILS_ROOT + "/config/config.local.yml")
else
  raw_config = File.read(RAILS_ROOT + "/config/config.yml")
end

Carlos A. da Silva
Nov 10, 2009

Hello!
Sometimes I use kind of config like you’ve explained. I also like to go with configatron to easy setup of the application.
http://github.com/markbates/configatron

Cheers, Carlos.
mathieul
Nov 10, 2009

Thanks for this post!

There is another dead simple solution presented by Ryan Bates in the Railscast #85 (http://railscasts.com/episodes/85-yaml-configuration-file) where he loads the configuration in a global constant from an initializer.
John Nunemaker
Nov 10, 2009

Interesting to see others are using something similar.

@mathieul – Ah, yeah, I forgot about that.
Mike Subelsky
Nov 10, 2009

Hi John, this is exactly what we do in OtherInbox and it works very well. We also use a custom version of the Settings plugin for variables that need to be changed while in production (http://beautifulpixel.com/svn/plugins/settings)

-Mike
gregf
Nov 10, 2009

Another vote for configatron here.
kris
Nov 10, 2009

Check out settingslogic. http://www.github.com/binarylogic/settingslogic
Trevor Turk
Nov 10, 2009

I actually do something similar that also works with Heroku. I linked to it from your article earlier this week already, but it’s relevant to this post, too :)

Steve Hoeksema

Nov 10, 2009

I use OStruct and YAML.

require 'ostruct'
require 'yaml'
settings = OpenStruct.new(YAML.load_file("#{RAILS_ROOT}/config/settings.yml"))
env_settings = settings.send(RAILS_ENV)
settings.common.update(env_settings) unless env_settings.nil?
::Settings = OpenStruct.new(settings.common)

common: &amp;common
  app_name: App
development:
  &lt;&lt;: *common
test:
  &lt;&lt;: *common
production:
  &lt;&lt;: *common

Then you can use Settings.app_name

John Nunemaker
Nov 12, 2009

@Steve – The only problem with OpenStruct is it doesn’t do nested hashes. If you nested any of the config you would have to do Settings.nested[:deeper_nested]. You might want to checkout mash which will do nested hashes.

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Authored by John Nunemaker (Noo-neh-maker), a programmer who has fallen deeply in love with Ruby. Learn More.

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