In my controller:
class WorkoutsController < ApplicationController
	 in_place_edit_for :w_set, :repetitions
	 in_place_edit_for :w_set, :weight
...


in my view:
          %td= in_place_editor_field s, 'repetitions'
          %td= in_place_editor_field s, 'weight'

The error:
RuntimeError in Workouts#edit

Showing app/views/workouts/edit.html.haml where line #23 raised:

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

where line 23 is: %td= in_place_editor_field s, 'repetitions'