How to use mongoid-paperclip to upload multiple images through nested model? - ruby-on-rails

Question

I have a rails app where I am trying to upload multiple images using nested_attributes but am running into great difficulty. The images don't seem to be saving to mongodb. I have followed this tutorial (though it seems lacking in detail): http://initializd.com/blog/2013/3/upload-multiple-files-with-html5-rails-mongoid-paperclip-and-google-cloud-storage
Basically, I have a form where a user is able to submit multiple listings (as nested attributes), and under each listing they are able to submit multiple images (also as nested attributes).
Here is my form:
The important part is the file_field_tag where the user is supposed to upload multiple images.
<%= nested_form_for #user, url: wizard_path, :html => { :multipart => true } do |f| %>
<h1 style="margin-bottom: 6%;"> Add Listings </h1>
<!-- nested fields -->
<%= f.fields_for :listings do |builder| %>
<div class="field form-group">
<%= builder.label :type %> <br />
<%= builder.select :type, options_for_select(listing_types), {}, { :class => 'form-control', :required => 'true' } %>
</div>
<div class="field form-group">
<%= builder.label :title %> <br />
<%= builder.text_field :title, class: 'form-control', required: 'true' %> <br />
</div>
<div class="field form-group">
<%= builder.label :description %> <br />
<%= builder.text_area :description, class: 'form-control', required: 'true' %>
</div>
<div class="field form-group">
<%= builder.label :url %> <br />
<%= builder.text_field :url, class: 'form-control', required: 'true' %>
</div>
<div class="field form-group">
<%= builder.label :zipcode %> <br />
<%= builder.text_field :zipcode, class: 'form-control', size: '24x4', required: 'true' %>
</div>
<div class="field form-group">
<%= label_tag "upload images" %> <br />
<%= file_field_tag('listing_images_attributes_file', multiple: true, name: "user[listings_attributes][images_attributes][][image]", :required => 'true') %>
</div>
<div class="field form-group">
<%= builder.link_to_remove "Remove this listing", :onclick =>"myFunction(this)" %>
<hr style="height: 2px; background-color: lightgray;">
</div>
<% end %>
<p style="margin-bottom: 15px;"><%= f.link_to_add "Add a listing", :listings %></p>
<div class="actions">
<%= f.submit "Continue", class: "btn btn-lg btn-primary" %>
</div>
<% end %>
Here are my models:
Listing Model:
class Listing
include Mongoid::Document
include Mongoid::Timestamps
field :title, type: String
field :type, type: String
field :description, type: String
field :url, type: String
field :zipcode, type: String
# association between listing and user
embedded_in :user
# each listing has many images
embeds_many :images, :cascade_callbacks => true
accepts_nested_attributes_for :images, :allow_destroy => true
end
Image Model:
class Image
include Mongoid::Document
include Mongoid::Timestamps
include Mongoid::Paperclip
field :listing_id, type: Integer # what is the purpose of this field exactly?
embedded_in :listing
has_mongoid_attached_file :image,
:path => ":rails_root/public/images/:id/:filename",
:url => "/images/:id/:filename"
end
Snippet from user controller update action (basically my create):
def update
#user = current_user
#have to include steps to validate zip code
case step
when :personal
#user.update_attributes(user_params)
when :listings
# should I build a listing as a default input?
# listing = #user.listings.build
#user.update_attributes(user_params)
end
render_wizard #user
end
def user_params
params.require(:user).permit(:first_name, :last_name, :zipcode, :bio, listings_attributes: [:title, :type, :description, :url, :zipcode,
{ images_attributes: [:image] }, :_destroy, :id])
end
Basically I am trying to get a user to be able to upload multiple listings, then multiple images under each listing. I wonder if this is possible using nested_attributes or will I have to handle the params manually? Also wondering whether my strong params are setup correctly. Here is a snippet from my server logs to show what my params look like:
Parameters: {"utf8"=>"✓", "authenticity_token"=>"HUpgUfukx3Rqb2Ye3su1/9ts4byC1BFrB3HOLXgQeJr8Vrcf9JyQYvR52FC5psLPZGD2x2DlzmlQRRgEXQWo2g==", "user"=>{"listings_attributes"=>{"0"=>{"type"=>"Airbnb", "title"=>"test", "description"=>"test", "url"=>"test", "zipcode"=>"test", "_destroy"=>"false", "id"=>"57a2b9ba9cd25d2d94110543"}}}, "listing"=>{"images_attributes"=>[{"image"=>#<ActionDispatch::Http::UploadedFile:0x000001016c2b20 #tempfile=#<Tempfile:/var/folders/vp/4hffkvd52gd317mgfqczqspm0000gn/T/RackMultipart20160804-11668-1fjlflq.jpg>, #original_filename="event1.jpg", #content_type="image/jpeg", #headers="Content-Disposition: form-data; name=\"listing[images_attributes][][image]\"; filename=\"event1.jpg\"\r\nContent-Type: image/jpeg\r\n">}]}, "commit"=>"Continue", "id"=>"listings"}
Sorry for the long description, but I was really hoping someone could answer this question. Thank you so much!