Ever wish you could visualize the relationships in your Rails application? You could grab a marker and head to the whiteboard. Or, you could have Ruby create a little graphical representation of your application in less time than it takes your finger to come off the Return key.

I originally found this trick on hackdiary, and I’ve modified it into a rake task.

Ingredients:

• Ruby on Rails
• OmniGraffle (or any diagraming application that can open *.dot files)
• Knowledge of Rake
• A backup of your app, just in case (you are using Subversion, aren’t you?)

Here’s the code:

desc "Create a graphical diagram of this app's models" 
task :graph do
  require "config/environment" 
  Dir.glob("app/models/*rb") { |f|
      require f
  }
  File.open("#{RAILS_ROOT}/models.dot", 'w') do |file|
    file.write "digraph x {" 
      Dir.glob("app/models/*rb") { |f|
        f.match(/\/([a-z_]+).rb/)
        classname = $1.camelize
        klass = Kernel.const_get classname
        if klass.superclass == ActiveRecord::Base
            puts classname
            klass.reflect_on_all_associations.each { |a|
                file.write classname + " -> " + a.name.to_s.camelize.singularize + " [label="+a.macro.to_s+"]" 
            }
        end
      }
    file.write "}"    
  end
end

To use:

1. Create a file in RAILS_ROOT/lib/tasks/graph.rake.
2. Drop in the above code.
3. Go to your terminal and (in the root of your application) type rake graph.
4. Now open OmniGraffle, and go to File > Open. Look for the file in your RAILS_ROOT directory called models.dot. Open it up.

Here’s what I got when I ran this script on SliceOfSites:

Link love goes to hackdiary, who originally posted this tip.