gistfile1.rbx

# e is for efficient. There's not really a way to eager load associations yourself
# without AR thinking you're trying to assign or create something.
attr_accessor :echildren

def self.find_all_efficiently
  categories = find(:all, :order => 'position ASC, name ASC').inject(Hash.new) do |h, c| 
    h[c.parent_id] ||= []
    h[c.parent_id] << c
    h
  end
  roots = categories[nil]
  roots.each { |r| r.echildren = categories[r.id] || []; r.echildren.each { |ch| ch.echildren = categories[ch.id] || [] } }
  roots
end