Rails ERD is a Rails plugin that allows you to easily generate a diagram based on your Active Record models. The diagram gives an overview of how your models are related. Having a diagram that describes your models is perfect documentation for your application.
The second goal of Rails ERD is to provide you with a tool to inspect your application's domain model. If you don't like the default output, it is very easy to use the API to build your own diagrams.
Rails ERD was created specifically for Rails 3. It uses Active Record's built-in reflection capabilities to figure out how your models are associated.
Here's an example entity-relationship diagram that was generated by Rails ERD:
Browse the gallery for more example diagrams.
See the installation instructions for a complete description of how to install Rails ERD. Here's a summary:
Install Graphviz 2.22+ (how?)
Add gem "rails-erd" to your application's Gemfile
Run bundle exec erd
More information can be found on Rails ERD's project homepage.
If you wish to extend or customise Rails ERD, take a look at the API documentation.
Rails ERD was created by Rolf Timmermans (r.timmermans at voormedia.com)
Copyright 2010-2013 Voormedia - www.voormedia.com
Rails ERD is released under the MIT license.