Display attempts to retain value of select when commit or patched

collection_select_example.html.erb

<!--I've tried the following -->
<%= f.collection_select(
                        :doctor_full_name, 
                        @resident.doctors, 
                        :full_name, 
                        :full_name,  
                        { selected: f.object.doctor_full_name, prompt: true }
                      ) %>

  <%= f.select(
                :doctor_full_name, 
                resident.doctors.map(&:full_name), 
                selected: f.object.doctor_full_name, 
                prompt: true
              ) %>