add gem to Gemfile

gem 'prailroady'

Use online preview

https://planttext.com/

Or install local

Mac users

Brew users can install via:

brew install graphviz

MacPorts users can install in via

sudo port install graphviz

Install Plantuml

http://plantuml.com/download

Install Atom Preview

https://atom.io/packages/plantuml-viewer

https://atom.io/packages/plantuml-preview

Run generate

prailroady -o models.pu -M # only model name
prailroady -o models.pu -M -l # with attributes

Then open models.pu using atom preview or use online preview.