Advanced Rails - Building Industrial-Strength Web Apps in Record Time

278 | Chapter 9: Incorporating and Extending Rails

Og::Mixin.autoload :Orderable, 'og/model/orderable'

# 4. Models must be loaded before Og starts

Dir[File.join(RAILS_ROOT, 'app', 'models', '*.rb')].each(&method(:load))

# 5. Read in database.yml and start Og

config = YAML.load_file(File.join(RAILS_ROOT, 'config', 'database.yml'))

$og = Og.start(config[RAILS_ENV].symbolize_keys)

This does several things to initialize Og:

1. First, as a sanity check, we use thegemmethod to specify the exact gem version
   we installed. As long as the gem specification (og.gemspec) specifies a version of
   0.50.0, that is the version that RubyGems will recognize. Therefore, we can
   refresh the Og gem from edge for minor changes without updating this line.


2. Theclass Objectblock is in place to work around an incompatibility between
   Ruby Facets and RailsDependencies. Og’s initialization methods load methods in
   Facets using therequiremethod. However,Dependenciesoverrides therequire
   method to keep track of the modules and classes being defined by files as they
   are required. The new version ofrequirecauses problems and prevents Og’s
   dependencies from being loaded properly.
   To resolve this, we temporarily disable all specialrequirefunctionality while
   loading Og. First, we store away a copy of the fully functionalrequire, with
   RubyGems andDependencies,asrequire_withrubygems. Then we aliasgem
   original_require(the no-frills standard Rubyrequire, which RubyGems help-
   fully aliases) asrequire, so that Og doesn’t notice any of the sneaky things we
   are doing. When Og is loaded, we can put the full-featuredrequirewith
   rubygems back into place.
   Notice that the actual call requiring Og needs to userequire_with_rubygemsso
   that it will find the gem. We do all of this manipulation so that Og’s nested calls
   torequire will use the Ruby version, not the RubyGems/Rails version.


3. In this example, we are mixing theOrderablemodule into our class; Og uses
   mixins to add behavior to model classes, where ActiveRecord would convention-
   ally use class methods (in this example,acts_as_list). UsingModule#autoload,
   we designate thatOg::Mixin::Orderablecan be found under Og’s source tree at
   og/model/orderable.rb.


4. As mentioned before, Og needs to see all of the models when it starts, so that it
   can inject them with Og model methods. (This is in contrast to the
   ActiveRecord and DataMapper method of requiring all models to inherit from a
   common base class.) But Rails usesDependenciesto lazy-load models; if we do
   not explicitly load them here, they will not exist until their name is referenced.