ActionController::UnknownFormat with format.js for ajax implementation (Rail 4)

Question

i try to use Ajax in my application with Rails 4. To send my js to the client i use :

   respond_to do |format|
        format.js 
   end

in my controller. But it's generated error "ActionController::UnknownFormat" i my controller. Someone can help me please ?

main_controller.rb:

class Oweb::MainController < ApplicationController
    def index
        .....
    end
    def setmagasinstatus
      begin                     
       @mag = Magasin.find(params[:id]) 
       if @mag.etatmagasin.lib == 'Ouvert'
            @mag.etatmagasin = Etatmagasin.where(lib: 'Fermé').first
       else
            @mag.etatmagasin = Etatmagasin.where(lib: 'Ouvert').first
       end 
      rescue ActiveRecord::RecordNotFound
       logger.error("Attempt to access invalid Magasin #{params[:id]}")
       redirect_to_index("Invalid Magasin")
      else
       @mag.save
       @mags = Magasin.where(user_id: current_user.id) 

       respond_to do |format|
            format.js 
       end

     end
    end
end

setmagasinstatus.js.erb :

page.replace_html("bloc_magasin", :partial => "listmagasins", :object => @mags)

layouts/application.html.slim:

doctype html
html
    head
        meta charset="utf-8"
        meta http-equiv="X-UA-Compatible" content="IE=edge"
        meta name="viewport" content="width=device-width, initial-scale=1.0"
        meta name="description" content=""
        meta name="author" content=""

        title = yield(:title)

        = stylesheet_link_tag "application"
        = csrf_meta_tags

    body
     .........
                = yield

        = javascript_include_tag "application"
        = yield :scripts

gemfile:

source 'https://rubygems.org'
# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.1.1'

group :development do
  gem 'mysql2'
end
group :production do
  gem 'pg'
end

gem 'sass-rails', '~> 4.0.3'

gem 'uglifier', '>= 1.3.0'

gem 'coffee-rails', '~> 4.0.0'

gem 'therubyracer',  platforms: :ruby


gem 'jquery-rails'

gem 'turbolinks'

gem 'jbuilder', '~> 2.0'

gem 'sdoc', '~> 0.4.0',          group: :doc

gem 'spring',        group: :development

gem 'devise', '~> 3.2.4'

gem 'slim-rails', '~> 2.1.4'

gem 'bootstrap-sass', '~> 3.1.1.1'

gem 'compass-rails', '~> 1.1.7'

gem 'simple_form', '~> 3.0.2'
gem 'activeadmin', github: 'gregbell/active_admin'

gem 'polyamorous', github: 'activerecord-hackery/polyamorous'

gem 'ransack', github: 'activerecord-hackery/ransack'

gem 'formtastic', github: 'justinfrench/formtastic'

 gem 'debugger', group: [:development, :test, :production]

gem 'geocoder'
gem 'gmaps4rails', '~> 2.1.2'

logs:

Started GET "/oweb/main/setmagasinstatus?id=3" for 192.168.56.1 at 2014-08-01 06:22:06 +0000
Processing by Oweb::MainController#setmagasinstatus as HTML
  Parameters: {"id"=>"3"}
Completed 406 Not Acceptable in 103ms

ActionController::UnknownFormat (ActionController::UnknownFormat):
  app/controllers/oweb/main_controller.rb:24:in `setmagasinstatus'


  Rendered /home/vagrant/.rvm/gems/ruby-2.1.1/gems/actionpack-4.1.1/lib/action_dispatch/middleware/templates/rescues/_source.erb (2.1ms)
  Rendered /home/vagrant/.rvm/gems/ruby-2.1.1/gems/actionpack-4.1.1/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.2ms)
  Rendered /home/vagrant/.rvm/gems/ruby-2.1.1/gems/actionpack-4.1.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.1ms)
  Rendered /home/vagrant/.rvm/gems/ruby-2.1.1/gems/actionpack-4.1.1/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (27.1ms)

Answer 1

Catch:

Your console log says:

Processing by Oweb::MainController#setmagasinstatus as HTML

In your controller action, you don't have supported HTML response. That's why you are facing error of UnknownFormat.

Solution:

Add format: "js" in your ajax call. For example:

$.ajax url: "/oweb/main/setmagasinstatus", data: 'id=' + id, format: 'js'

Answer 2

If you can use link_to helper function to call action of your controller, in your case Oweb::MainController#setmagasinstatus adding :remote => true to link_to helper will solve the issue.

For example if you have a link to your action and want to get response in ajax the following code will create the link to that action:

<%= link_to your_link_name, setmagasinstatus_path(:params), :remote => true %>

Here is a dead easy sample https://coderwall.com/p/kqb3xq/rails-4-how-to-partials-ajax-dead-easy

Answer 3

HTML

Looks like the problem is you're sending an HTML request for whatever reason:

Oweb::MainController#setmagasinstatus as HTML

I'd surmise the "unkown format" error will therefore be caused by your lack of definition for the html mime-type in your action. I'd imagine this would work to resolve the error at surface-level:

 respond_to do |format|
     format.js 
     format.html
  end

---

Ajax

If the above is correct, the question then turns to "why is an HTML mime-type being sent?"

Due to not being able to see your actual Ajax code, I'd recommend the problem will either be that you're just sending a standard HTTP request (ajax is XHR); or you'll have an issue with the declaration with the ajax request

You must remember that Ajax (Asynchronous Javascript And XML) is meant to send a request on your behalf -- like a pseudo browser. This means if you want to send an ajax request, it has to be done through Javascript (hence the format.js mime type handler)

--

Personally, I think you're not sending an ajax request, although it could also be that you're sending a different dataType, such as JSON