Mod Cons (pl. n.). 1. Slang abbreviation of Modern Conveniences. 2. A great way to refer to the Modern Conveniences of Modular Configuration.

Modular, decentralized configuration declarations for Ruby. Every module, class, or file declares its own configurable parameters, which are merged into the (optionally) global configuration object.

<img src=“https://secure.travis-ci.org/mbklein/mod-cons.png” />

In foo.rb:

ModCons::Config.declare(:foo) do
  url nil
  cert_file nil
  key_file nil
  key_pass ''
end

class Foo
  def initialize
    @config = ModCons::Config.foo
  end

  def get_thing
    do_something_with(@config.url)
    ### Or, forget the instance variable and go global ###
    do_something_with(ModCons::Config.foo.url)
  end
end

In bar.rb:

ModCons::Config.declare(:bar) do
  url nil
  credentials do # In-place sub-configuration declaration!
    username nil
    password nil
  end
end

In baz.rb:

ModCons::Config.declare(:baz) {  key 'value'  }

ModCons::Config.configure do
  foo do
    url 'http://example.com/path/to/bar/resource'
    cert_file '/path/to/cert.cer'
    key_file '/path/to/cert.key'
    key_pass 'certpassword'
  end

  bar do
    url 'http://example.com/path/to/bar/resource'
    credentials.username 'validuser'
    credentials.password 'validpass'
    ### OR ###
    credentials do
      username 'validuser'
      password 'validpass'
    end
  end

  baz.key 'Some other value'
end

ModCons::Config.configure({
  :foo => {
    :url => "http://example.com/path/to/bar/resource",
    :cert_file => "/path/to/cert.cer"
    :key_file => "/path/to/cert.key",
    :key_pass => "certpassword",
  },
  :bar => {
    :url => "http://example.com/path/to/bar/resource",
    :credentials => {
      :username => "validuser",
      :password => "validpass"
    }
  },
  :baz => { :key => "Some other value" }
});

You can even have it create a skeleton config file for you:

File.write('config.rb', 'w') { |f| f.write(ModCons::Config.template) }

# Produces a file called config.rb containing the following:
ModCons::Config.configure do
  bar do
    credentials do
      password nil
      username nil
    end
    url nil
  end
  baz.key "value"
  foo do
    cert_file nil
    key_file nil
    key_pass ""
    url nil
  end
end

Want to keep resources external to the configuration object in sync with configuration changes?

ModCons::Config.declare(:quux) do
  email nil
  config_changed do |config|
    some_global_object.email_address = config.email
  end
end

ModCons::Config is just a global instance of ModCons::Configuration. Your class, module, or application can define its own arbitrarily-scoped copy instead.

require 'forwardable'

class Foo
  extend Forwardable
  def_delegator :@config, :configure

  def initialize
    @config = ModCons::Configuration.declare(:config) do
      key1 'default1'
      key2 'default2'
    end
  end

  def key_1
    @config.key1
  end
end

f = Foo.new
f.configure { key1 'value1' }
puts f.key_1

• Configuration property names must begin with a letter, and can only contain letters, numbers, and underscores.

• Due to the self-declaring, self-configuring, meta-programmed nature of ModCons::Configuration, the following tokens are not available as configuration property names:

  • class

  • config_changed

  • configure

  • declare

  • initialize

  • inspect

  • instance_eval

  • method_missing

  • methods

  • new

  • template

  • to_hash

  • to_s

• 0.1.1 Initial public release

• 0.2.0 Add ModCons::Configuration#post_config to allow manual invocation of post configuration listeners

• Check out the latest master to make sure the feature hasn’t been implemented or the bug hasn’t been fixed yet

• Check out the issue tracker to make sure someone already hasn’t requested it and/or contributed it

• Fork the project

• Start a feature/bugfix branch

• Commit and push until you are happy with your contribution

• Make sure to add tests for it. This is important so I don’t break it in a future version unintentionally.

• Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

Copyright © 2011 Michael B. Klein. See LICENSE.txt for further details.