CORS error for rails API -

i building rails api , when send request app (on different subdomain api) following response:

xmlhttprequest cannot load http://api.myapp.dev/v1/posts/create. request header field content-type not allowed access-control-allow-headers.

i don't understand why happening, since in rails controller have set headers['access-control-allow-headers'] = '*'.

my app/routes.rb file:

rails.application.routes.draw   namespace :v1, defaults: {format: 'json'}     # take care of cors     match "*all", to: "api#cors_preflight_check", via: [:options]      # routes posts     'posts(/index)', :to => 'posts#index'     post 'posts/create'     delete 'posts/:id', :to => 'posts#destroy'     'posts/show'     put 'posts/:id', :to => 'posts#update'      # routes post comments     'posts/:post_id/comments(/index)', :to => 'comments#index'     post 'posts/:post_id/comments/create', :to => 'comments#create'     delete 'posts/:post_id/comments/:id', :to => 'comments#destroy'     put 'posts/:post_id/comments/:id', :to => 'comments#update'    end end 

my app/controllers/v1/api_controller.rb file:

module v1     class apicontroller < applicationcontroller     skip_before_filter :verify_authenticity_token     protect_from_forgery with: :null_session     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'] = '*'       headers['access-control-request-method'] = '*'       headers['access-control-allow-headers'] = '*'       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'] = '*'         headers['access-control-request-method'] = '*'         headers['access-control-allow-headers'] = '*'         headers['access-control-max-age'] = '1728000'         render :text => '', :content_type => 'text/plain'       end     end   end end 

what problem be?

honestly easiest thing use this , set configuration in config/application.rb file.