Rails accepts_nested_attributes_for多态强参数

Question

I have an article model that has a polymorphic association with an attachment table.

In the new article form I require the user to be able to upload attachments.

The code works other than the strong params as I have no idea what to place as the strong params for the polymorphic relationship.

def create
  @article = Article.build(article_params)
  @article.user_id = current_user.id
  if @article.save
    params[:article_attachments]['attachment'].each do |a|
      @article.attachments.create!(:file => a)
    end

    respond_to do |format|
      format.html {redirect_to article_path(@article)}
      format.js
    end
  else
    render 'new'
  end
end

private
  # Never trust parameters from the scary internet, only allow the white list through.
  def article_params
    params.require(:article).permit(:content, attachments_attributes: [])
  end

The attachment model is structured as follows:

Attachment
=> Attachment(id: integer, file: string, attachable_id: integer, attachable_type: string, created_at: datetime, updated_at: datetime)

The nested form is:

<div class="uploader pull-left" >
  <%= f.fields_for :attachments do |builder| %>
    <%= builder.file_field :file, :multiple => true, accept: 'image/jpeg,image/gif,image/png', name: "discussion_attachments[attachment][]" %>
  <% end %>
</div> 

The params hash is as follows:

{"utf8"=>"✓", "authenticity_token"=>"m84LL1D05LCsivXuASukGgcDoVhTvxhVuDThv9Q2iDRS/AMOeMvQArc0mpMZJSsW887R2krWu85Xm1v9+WQ8bQ==", "article"=>{"content"=>""}, "attachments"=>{"file"=>[#<ActionDispatch::Http::UploadedFile:0x007f0918ffb720 @tempfile=#<Tempfile:/tmp/RackMultipart20150810-3911-1rsq9lz.JPG>, @original_filename="YourPhoto_0001.JPG", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"attachments[file][]\"; filename=\"YourPhoto_0001.JPG\"\r\nContent-Type: image/jpeg\r\n">, #<ActionDispatch::Http::UploadedFile:0x007f0918ffb338 @tempfile=#<Tempfile:/tmp/RackMultipart20150810-3911-i1ztf2.JPG>, @original_filename="YourPhoto_0002.JPG", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"attachments[file][]\"; filename=\"YourPhoto_0002.JPG\"\r\nContent-Type: image/jpeg\r\n">]}, "commit"=>"Submit", "controller"=>"articles", "action"=>"create"}

Answer 1

It seems to me that you are trying to add multiple file attachments using Carrierwave .

In order for this to work you need to specify the following inside of your article_params ...

def article_params
  params.require(:article).permit(:content, attachments_attributes: [:id, :attachable_id, :name])
end

As you can see you need to specify 3 params. Both :id and :attachable_id are needed to specify the association/relationship and :name is the name of the file/path.

I hope this helps you out, Tim.