Rails 3.0/3.2: Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id
ruby-on-rails, ruby-on-rails-3, ruby-on-rails-3.2
Solution
The message:
"Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id"
Is the standard message in Rails that tells you that you tried to invoke `.id` on a `nil` value.
So if `@subject` is nil, then it's normal, appropriate behavior to get that message if you try to call `@subject.id`.
I'd recommend that in the view file you take into account that `@subject` may be `nil` and address it in how you present the information. Look at the code and think what you should be presenting in the view there if `@subject` is `nil`.
Problem
I'm following the Kevin Skoglund tutorial Ruby on Rails 3 Essential Training, which was written for rails 3.0, though I am currently using 3.2. It uses the following method in the pages_controller with a before_filter to display only the pages which belong to the parent subject. The tutorial explicitly uses .find_by_id because if the result is nil it "will not return an error". However I get the "Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id" error when trying to view a page where @subject has been set to nil. ``` def find_subject if params[:subject_id] @subject = Subject.find_by_id(params[:subject_id]) end end ``` The actual code that is causing the error is: ``` def list @pages = Page.order("pages.position ASC").where(:subject_id => @subject.id) end ``` Is this something that has changed since 3.0? If so, what would be the correct way to implement this functionality in 3.2?