carrierwave - Rails form not retaining nested attributes upon failed submission -

i have articles form lists articles, includes form submit new article nested fields attaching photos.

the form works , saves both article , photos.

when validation fails render index action displays validation errors correctly.

when render index action incorrect form data displayed correctly selected photos not retained user has correct data entry , reattach photos again.

this problem users tend correct form data submit without noticing photos have not been attached.

def index   @article  = article.new   @articles = article.all end   def create   @article = article.new(discussion_params)   @article.user_id = current_user.id   @articles = article.all    if @article.save     redirect_to articles_path   else     render "index"   end end  private    # never trust parameters scary internet, allow white list through.   def article_params     params.require(:article).permit(:content, attachments_attributes: [:id, :file, :_destroy])   end 

attachment.rb

class attachment < activerecord::base   mount_uploader :file, attachmentuploader   belongs_to :attachable, polymorphic: true end 

new discussion controller params

# never trust parameters scary internet, allow white list through. def article_params   params.require(:article).permit(:content, attachments_attributes: [:id, :file, :file_cache, :_destroy]) end 

params passed submitting article

parameters: {"utf8"=>"✓", "authenticity_token"=>"zwva0z7q7qj/dihsatdpihkegy0k2jgtc1arwvj5rizqr/oqk/xqrpixpjidy1gzugtyrgyhvu3uujn47cb+iw==", "article"=>{"content"=>"", "attachments_attributes"=>{"0"=>{"file"=>#<actiondispatch::http::uploadedfile:0x007f5dce86e8a8 @tempfile=#<tempfile:/tmp/rackmultipart20151003-3227-1gsru7x.jpg>, @original_filename="yourphoto_0001.jpg", @content_type="image/jpeg", @headers="content-disposition: form-data; name=\"article[attachments_attributes][0][file]\"; filename=\"yourphoto_0001.jpg\"\r\ncontent-type: image/jpeg\r\n">, "file_cache"=>"1443854078-3227-6970/yourphoto_0001.jpg", "id"=>"", "_destroy"=>"false"}}}, "commit"=>"submit"}