Ajax does not work(format: :js) after upgrading to Rails 4.2.9

Question

Code

I just upgraded Rails from 4.1.11 to 4.2.9, and everything works fine except ajax!

I got a link works with ajax which looks like below:

<%= link_to("hide", admin_course_path(id: course.id, hide: "true"), remote: true, format: :js, method: :put) %>

And backend looks like this:

class Admin::CoursesController < .....
  respond_to :html, :json, :js

  def update
    @course = Course.find(params[:id])

    if params[:hide]
      @course.update_attributes(hide: true)
    else
      .....
    end

    respond_with([:admin, @course])
  end
end

Problem

It should be a js ajax, but now I receive error like below:

Started PUT "/admin/courses/11111?hide=true" for ::1 at 2017-08-24 12:57:49 +0800
Processing by Admin::CoursesController#update as JS
  Parameters: {"hide"=>"true", "id"=>"11111"}
  User Load (0.4ms)  SELECT  `users`.* FROM `users` WHERE `users`.`id` = 21808  ORDER BY `users`.`id` ASC LIMIT 1
  Course Load (0.4ms)  SELECT  `courses`.* FROM `courses` WHERE `courses`.`id` = 11111 LIMIT 1
Completed 500 Internal Server Error in 17ms (ActiveRecord: 2.1ms)

NoMethodError - undefined method `ref' for nil:NilClass:
  actionpack (4.2.9) lib/action_controller/metal/rendering.rb:9:in `process_action'
  actionpack (4.2.9) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
  activesupport (4.2.9) lib/active_support/callbacks.rb:117:in `call'
  activesupport (4.2.9) lib/active_support/callbacks.rb:555:in `block (2 levels) in compile'
  activesupport (4.2.9) lib/active_support/callbacks.rb:505:in `call'
  activesupport (4.2.9) lib/active_support/callbacks.rb:92:in `__run_callbacks__'
  activesupport (4.2.9) lib/active_support/callbacks.rb:778:in `_run_process_action_callbacks'
  activesupport (4.2.9) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (4.2.9) lib/abstract_controller/callbacks.rb:19:in `process_action'
  actionpack (4.2.9) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.2.9) lib/action_controller/metal/instrumentation.rb:32:in `block in process_action'
  activesupport (4.2.9) lib/active_support/notifications.rb:164:in `block in instrument'
  activesupport (4.2.9) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.2.9) lib/active_support/notifications.rb:164:in `instrument'
  actionpack (4.2.9) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.2.9) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  activerecord (4.2.9) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.2.9) lib/abstract_controller/base.rb:137:in `process'
  actionview (4.2.9) lib/action_view/rendering.rb:30:in `process'
  actionpack (4.2.9) lib/action_controller/metal.rb:196:in `dispatch'
  actionpack (4.2.9) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.2.9) lib/action_controller/metal.rb:237:in `block in action'
  actionpack (4.2.9) lib/action_dispatch/routing/route_set.rb:74:in `dispatch'
  actionpack (4.2.9) lib/action_dispatch/routing/route_set.rb:43:in `serve'
  actionpack (4.2.9) lib/action_dispatch/journey/router.rb:43:in `block in serve'
  actionpack (4.2.9) lib/action_dispatch/journey/router.rb:30:in `serve'
  actionpack (4.2.9) lib/action_dispatch/routing/route_set.rb:817:in `call'

Maybe the problem is at the line actionpack (4.2.9) lib/action_controller/metal/rendering.rb:9:in process_action.

After digging into actionpack deeper, I found that the process_action defined as:

# Before processing, set the request formats in current controller formats.
def process_action(*) #:nodoc:
  self.formats = request.formats.map(&:ref).compact
  super
end

So it means the request from ajax can't get the formats. I went on to print request.format & request.formats, first one showed text/javascript, but second one showed nothing. I don't know why the request.formats is missing.

I also upgrade jquery-rails to 4.1.1(the one that related to ajax), but no luck.

If anyone know about this, please give some advice. Much appreciated:)

---

Info

• rails: 4.2.9
• jquery-rails: 4.1.1
• responders: 2.4.0

---

Answer 1

After a long period of testing, I found that you should add format: :js in the path helper.

<%= link_to("hide", admin_course_path(id: course.id, hide: "true", format: :js), remote: true, method: :put) %>

It will transform to /admin/course/:id.js automatically, and cause no errors!