title: belongs_to association -- how do I call it?
body: <p>Silly question, but I can't find an example . . .</p>
  
  <p>My User model has_many Comments. My Comments model belongs_to User. The Comments table has a column user_id, which I've included in my db:seeds file. Every comment has a user_id.</p>
  
  <p>So how do I refer to a comment's user? "Comment.user" seems like it should work, but I keep getting error messages saying user is nil, or an undefined method.</p>
  
  <p>In particular, I want to refer to attributes of user through comment, such as comment.user.avatar.</p>