Question: I have a user model and a profile model.

user `has_one :profile`  

profile `belongs_to :user`

On the "show" view of the profile, there's an input field that only the owner of the profile should see. I currently have it limited to where only a logged-in user can see it, but I need it to go further and only appear visible to the user who owns that particular profile.

I am using the following to limit the view to only logged in users: <% if logged\_in? %>.

Answer: 
I'm just guessing here, but I'm assuming that you're using restful\_authentication because of the logged\_in method. If you are, you can use current\_user to filter this out.

Example: (assuming that you have a @user variable)

show field
Set a SESSION variable with the user name when the user is authenticated. Then, in every single page when you check if the session is set, check if that user (as set in the session variable) has access to what that page contains OR display only that part to which only that user has access.