Using checkbox for a multiple-value parameter in Rails

This wasn't obvious. Thanks to satish on rails I learned this is the way to do it:

 <input type="checkbox" name="customer[preferences][]" value="yellow"/>
 <input type="checkbox" name="customer[preferences][]" value="blue"/>
 etc

The extra [] at the end of the parameter name makes all the difference. In your controller, you can now reference

  params[:customer][:preferences]

and get a list.