fields for instead form for (solved problem with sibmission button)

app/views/exercises/_file_form.html.slim

@@ -1,4 +1,4 @@
-= form_for(file) do |f|
+= fields_for(file) do |f|
   li.panel.panel-default
     .panel-heading role="tab" id="heading"
       a.file-heading data-toggle="collapse" data-parent="#files" href="#collapse#{file.id}"
@@ -36,8 +36,6 @@
           .form-group
             = f.label(:role, t('activerecord.attributes.file.weight'))
             = f.number_field(:weight, class: 'form-control', min: 1, step: 'any')
-
-        /render ace editor
         - unless file.new_record?
           = render partial: 'ace', locals: { exercise: @exercise, file: file }
 

app/views/exercises/_form.html.slim

@@ -29,13 +29,11 @@
       = f.check_box(:allow_file_creation)
       = t('activerecord.attributes.exercise.allow_file_creation')
   h2 = t('activerecord.attributes.exercise.files')
-
   ul#files.list-unstyled.panel-group
     - @exercise.files.each do |file|
-      = render partial: 'file_form', locals: { file: file }
-
+      = render partial: 'file_form', locals: {file: file}
   a#add-file.btn.btn-default.btn-sm.pull-right href='#' = t('.add_file')
-
   ul#dummies.hidden
-    = render partial: 'file_form', locals: { file: CodeOcean::File.new }
+    = render partial: 'file_form', locals: {file: CodeOcean::File.new}
   .actions = render('shared/submit_button', f: f, object: @exercise)
+