title: Preventing duplicate model objects with nested forms in rails 3
body: <p>I have a form set up for a Recipes model that accepts_nested_attributes_for Ingredients. The form and saving works fine, however, I want to check for the existence of each Ingredient in the database. The form seems to be creating new records for ingredients, even if they already exist in the database.</p>
  
  <p>Recipes and Ingredients are related using a 'has_many :through' relationship. Is there a clean way to make sure that ingredients are duplicated when the form is submitted, but the relationships are still established?</p>