== Create or Select

I wanted a form field that I could have a user fill in, and it would either select the matching thing (as in a select box) or create a new one with the attribute.

For instance, if you have say, our friend the blog, and that has Post which belongs_to Category.  My goal was a text field for category (as opposed to the usual select) that will allow both an existing value, or a new one.

I also wanted it to be safe. My first attempts at this ended rather poorly, and just didn't feel right. I tried both some madness on the models, and some transactions in the controller when saving.  The transactions do work, but you wind up with a lot of book keeping for such a small thing.

The approach I settled on (as you will see) is using nested attributes, but in reverse. All the examples I found assumed you wanted the has_many end of the relation in the form.  Some time in irb later, I nailed it. (Or got it working, anyway)

A bit more detail at http://ajvargo.com/2010/10/create-or-select-a-value-via-nest-resources/