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CORS in Rails 4 APIs
class API::V1::BaseController < ApplicationController
skip_before_filter :verify_authenticity_token
before_filter :cors_preflight_check
after_filter :cors_set_access_control_headers
def cors_set_access_control_headers
headers['Access-Control-Allow-Origin'] = '*'
headers['Access-Control-Allow-Methods'] = 'POST, GET, PUT, DELETE, OPTIONS'
headers['Access-Control-Allow-Headers'] = 'Origin, Content-Type, Accept, Authorization, Token'
headers['Access-Control-Max-Age'] = "1728000"
end
def cors_preflight_check
if request.method == 'OPTIONS'
headers['Access-Control-Allow-Origin'] = '*'
headers['Access-Control-Allow-Methods'] = 'POST, GET, PUT, DELETE, OPTIONS'
headers['Access-Control-Allow-Headers'] = 'X-Requested-With, X-Prototype-Version, Token'
headers['Access-Control-Max-Age'] = '1728000'
render :text => '', :content_type => 'text/plain'
end
end
end
Rails.application.routes.draw do
namespace :api, :defaults => {:format => :json} do
namespace :v1 do
controller :whatever, path: '/whatever' do
match 'post_action', via: [ :post, :options]
end
end
end
end
class API::V1::WhateverController < API::V1::BaseController
def upload
# Do complicated super secret stuff
render json: { success: true }
end
end

Thanks so much for posting this.
Just a little note in case anyone has the problem, I was performing post using Angular's $http.post, and needed to add 'content-type' to the allowed headers on the preflight check, I guess since angular's post always automagically adds json as the content type. Otherwise this worked like a charm!

Thanks for the gist!

I have an issue though. It seems that the OPTION request worked, because I get 200 OK from my Angular app. But that's all I get, I don't get any response with the data I need.

Any idea how to solve this?

Braidio commented Apr 17, 2015

@sebastialonso Same here. Any luck with that?

@sebastialonso , Please have a look at line 22

render :text => ''

Change the above to send same response to all Options reqs. You can extend this by setting a necessary handler instead of render.

jnwelzel commented May 4, 2015

So you're basically all-round disabling the same-origin policy?

I'm getting this error:

XMLHttpRequest cannot load http://localhost:3000/api/auth/google_oauth2. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access.

Any suggestions?

I have same error like @urbanvikingr
I'm use Rails 4 for backend and Angular for the frontend

Please help :(

Hi, finally I solve the problem
the problem is in my Rails app

I found this:
https://github.com/cyu/rack-cors

@urbanvikingr I hope it can solve your problem too

snappa commented Sep 17, 2015

Wow, thank you so much! This helped me over the hurdle testing my ionic app. I know I have some tweaking to get this dialed in just right but this was immensely helpful!

How can you do this with the assets pipeline?

panchew commented Oct 10, 2015

Thank you very much for posting this.
It worked perfectly for me.

npetkov commented Feb 24, 2016

Just in case someone stumbles upon this gist, here's a more brief solution to the problem.

  1. Tell rails (rack) what to do with OPTIONS requests:

    Append this simple line to the end of your routes.rb file:

      match '*path', via: [:options], to:  lambda {|_| [204, {'Content-Type' => 'text/plain'}, []]}

    What does it do? It will handle OPTIONS requests on all of your routes, responding with no content and the appropriate Access-Control headers. The response is rendered on rack level, so you won't have to think about this on higher levels (e.g. controllers).

  2. Add the headers you need via rack-cors:

    You can insert this snippet in environments/development.rb.

    config.middleware.insert_before 0, 'Rack::Cors', logger: (-> { Rails.logger }) do
      allow do
        origins 'localhost:3000'
    
        resource '*',
          headers: :any,
          methods: [:get, :post, :delete, :put, :patch, :options, :head],
          max_age: 0
      end
    end

    That's it really.

Awesome! thanks.

@npetkov - thank you very much!

nshoes commented Jul 20, 2016

@npetkov - 👍

@npetkov - thanks! For the first part I added this to routes and it got everything working:

 Rails.application.routes.draw do
   ...
   match '*path', via: [:options], to:  lambda {|_| [204, {'Access-Control-Allow-Headers' => "Origin, Content-Type, Accept, Authorization, Token", 'Access-Control-Allow-Origin' => "*", 'Content-Type' => 'text/plain'}, []]}
end

That solved the problem. What is the second part for

cesc1989 commented Dec 6, 2016

Thanks a lot @npetkov

And thank you @davidcotter too

I opened an issue for that rails/rails#27655

Thanks

I get a Rack lint error when trying to pass any headers with a 204.

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