NestedHasManyThrough
====================

This plugin makes it possible to define has_many :through relationships that
go through other has_many :through relationships, possibly through an
arbitrarily deep hierarchy. This allows associations across any number of
tables to be constructed, without having to resort to find_by_sql (which isn't
a suitable solution if you need to do eager loading through :include as well).

It is hoped that this feature will in time be applied to the Rails core, after
which this plugin will become unnecessary.
See: http://dev.rubyonrails.org/ticket/6461

Example
-------

class Pub < ActiveRecord::Base
  belongs_to :city
end

class City < ActiveRecord::Base
  belongs_to :country
  has_many :pubs
end

class Country < ActiveRecord::Base
  belongs_to :planet
  has_many :cities
  has_many :pubs, :through => cities
end

class Planet < ActiveRecord::Base
  belongs_to :star_system
  has_many :countries
  has_many :cities, :through => :countries

  # Now we go through a has_many :through association -
  # something that wasn't previously possible
  has_many :pubs, :through => :cities
end

class StarSystem < ActiveRecord::Base
  has_many :planets
  has_many :countries, :through => :planets
  
  # We can also use a has_many :through association for the source
  # association; in this case, Country#pubs 
  has_many :pubs, :through => countries
end