The MongoDB classes do not come with default generators for Rails applications. In order to use the rails generate commands, you can use the indirect rails3-generators project available at


  1. Download the generators into your application’s lib folder:
    cd myapp
    git clone git:// lib/generators`
  2. Install the rails3-generators gem
    gem install rails3-generators
  3. Add this to your project’s Gemfile
    gem 'rails3-generators'


rails generate model ModelName --orm=mongo_mapper