Rails: File to Upload does not get passed from Form to the controller

Question

This is the Form. All of the fields get passed (and saved) except the one containing the File. I have checked that using the

render plain: params[:article].inspect   method

giving out this (I have entered the value "n" for all fields):

{"country"=>"n", "region"=>"n", "town"=>"n", "street"=>"n", "company"=>"n", "title"=>"n", "content"=>"n"}

I am leaving out superfluous fields here to make the Form shorter:

<%= form_for(@article, html: { multipart: true }) do |f| %>
  <%= render 'shared/error_messages', object: f.object %>       
          <%= f.label :country %>
          <%= f.text_field :country, :required => true, 
          placeholder: "enter country" %>
          </div>                  
      <%= f.label :content %>
      <%= f.text_field :content, :required => true, placeholder: "town..." %>
            </div>  
         </div>
     </div>         
  </div>       
<span class="picture">
   <%= form_for @article, html: { multipart: true } do |f| %>
     <%= f.text_field :title %>
     <%= fields_for :pictures do |ff| %>
     <%= ff.file_field :picture %>
   <% end %>
  <% end %> 
</div>

I have also tried the slight variation here, but no change

http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-fields_for

The create method at the Controller is like this:

def create
      @article = current_user.articles.build(article_params)
    if @article.save
      flash[:success] = "Article created!"
      redirect_to root_url
    else
      render 'articles/new'
    end
  end

and yes, the new method in the Articles controller, is like I was indicated by peers here:

def new
    @article  = current_user.articles.build 
    @article.pictures.build
  end

The Article Model

class Article < ActiveRecord::Base
  belongs_to :user
  has_many :pictures
  accepts_nested_attributes_for :pictures, allow_destroy: true

And the pictures Model

class Picture < ActiveRecord::Base
  belongs_to :article
 mount_uploader :picture, PictureUploader

end

Answer 1

Change your <%= fields_for :pictures do |ff| %> <%= fields_for :pictures do |ff| %> to <%= f.fields_for :pictures do |ff| %> <%= f.fields_for :pictures do |ff| %>