remove_target!

# File activerecord/lib/active_record/associations/has_one_association.rb, line 78
        def remove_target!(method)
          case method
          when :delete
            target.delete
          when :destroy
            target.destroyed_by_association = reflection
            target.destroy
          else
            nullify_owner_attributes(target)
            remove_inverse_instance(target)

            if target.persisted? && owner.persisted? && !target.save
              set_owner_attributes(target)
              raise RecordNotSaved, "Failed to remove the existing associated #{reflection.name}. "                                      "The record failed to save after its foreign key was set to nil."
            end
          end
        end