tibbon/Rails-3-has-and-belongs-to-many-issue — pull request #1 by hardbap (2012-01-12 21:36:39+00:00)
Title: Use #create instead of #new when creating relationship

#new will return an instance of Project but it has no idea about the relationship. To have rails magically create this you need to use the #create method instead.

I've added some validation to Project so you can see how this will work.