如何将任意（非模型属性）值传递给rails操作？

I have a unidirectional relationship model between users (users have many relationships) which holds the ids of two given users along with user a's nickname for user b. I want to use a form to allow users to pass in an e-mail address of another user and the nickname. If a user with that email exists, then create a relationship between the users. If no user matches, create a new 'phantom' user with that email and then build the relationship. I have a unidirectional relationship model betw