gistfile1.rb

#!/usr/bin/env ruby
require "config/environment"
Dir.glob("app/models/*rb") { |f|
    require f
}

puts %{digraph x \{ 
  has_many1 [shape=point]
  has_many2 [shape=point]
  has_many1 -> has_many2 [label="Has many", color=red]
  belongs_to1 [shape=point]
  belongs_to2 [shape=point]
  belongs_to1 -> belongs_to2 [label="Belongs to", color=blue]
  has_and_belongs_to_many1 [shape=point]
  has_and_belongs_to_many2 [shape=point]
  has_and_belongs_to_many1 -> has_and_belongs_to_many2 [label="HaBtM", color=green]
  has_one1  [shape=point]
  has_one2  [shape=point]
  has_one1 -> has_one2 [label="Has one", color=gray]
  node [shape=box, style=filled, fillcolor=lightgray, width=2.5] 
}
Dir.glob("#{RAILS_ROOT}/app/models/*rb") { |f|
  f.match(/\/(\w+).rb/)
  classname = $1.camelize
  classname = $1 + 'QR' if classname =~ /(\w+)Qr$/ # total hack for question response models
  klass = Kernel.const_get classname
  obj = klass.new rescue next
  if obj.kind_of? ActiveRecord::Base
      puts classname
      klass.reflect_on_all_associations.each { |a|
        att = case a.macro
                when :has_many : 'color=red, '# label="#{a.macro.to_s.humanize}"
                when :belongs_to : 'color=blue, '
                when :has_and_belongs_to_many : 'color=green, '
                when :has_one : 'color=gray, '
                else 'color=black, '
                end
        puts %{ #{classname} -> #{a.name.to_s.camelize.singularize} [ #{att} fontsize="8"]}
      }
  end
}
puts "}"