Rails 4 not changing post method to patch

Question

I am trying to submit a form, but if I just put form_for @classroom I get a "No route matches [POST]" error.

Now with the code posted below, I get the wrong url in the form. If I change the url manually in the browser it goes through, and I guess I could do that via javascript, but... why... is... this... happening..?

Until yesterday everything was working fine. I even tried rolling back to the things I changed but I can't seem to track what is going wrong.

routes.rb

patch 'classrooms/:id/update' => "classrooms#update", as: :update_classroom
resources :classrooms, except: :update

form from rails end

<%= form_for(update_classroom_path(@classroom), method: "patch") do |class_f| %>

form in browser

<form action="/classrooms/23/edit" accept-charset="UTF-8" method="post">
<input name="utf8" type="hidden" value="✓">
<input type="hidden" name="_method" value="patch">
<input type="hidden" name="authenticity_token" value="******">

rake routes

        absences POST   /absences(.:format)                   absences#create
                 POST   /classrooms/:id/getAbsences(.:format) classrooms#getAbsences
update_classroom PATCH  /classrooms/:id/update(.:format)      classrooms#update
      classrooms GET    /classrooms(.:format)                 classrooms#index
                 POST   /classrooms(.:format)                 classrooms#create
   new_classroom GET    /classrooms/new(.:format)             classrooms#new
  edit_classroom GET    /classrooms/:id/edit(.:format)        classrooms#edit
       classroom GET    /classrooms/:id(.:format)             classrooms#show
                 DELETE /classrooms/:id(.:format)             classrooms#destroy
            root GET    /                                     pages#start

Answer 1

Just to answer your question from title, I think your form method is "PATCH" indeed. Refer to the guide http://guides.rubyonrails.org/form_helpers.html about how rails makes a patch form.

The Rails framework encourages RESTful design of your applications, which means you'll be making a lot of "PATCH" and "DELETE" requests (besides "GET" and "POST"). However, most browsers don't support methods other than "GET" and "POST" when it comes to submitting forms.

Rails works around this issue by emulating other methods over POST with a hidden input named "_method", which is set to reflect the desired method:

Answer 2

To add a bit of specificity, to Tashow's answer above (which set me on the right track), I had some hidden fields that look'd like this, in a nested form.:

<%= hidden_field_tag("Classroom[classroom_teachers_attributes][]", nil) %>
<%= hidden_field_tag("Classroom[classroom_teachers_attributes][]", '') %>

Once I got rid of these, everything began working properly again. (There still remained similar-looking <input> tags generated by fields_for, etc.)