Hi all!

I have a multi-step form inspired by this railcast that has 3 file upload images. However when I upload an image I receive an error can't dump File.

From searching in forums I saw posts saying that saving a file uploads in the session doesn't work so I need to use something like this:

Code:
   unless @post.valid?
      @post.assets.first.attachment.clear
      @post.assets.first.attachment.queued_for_write.clear
    end

This however doesn't seem to work. Should I look through the three file uploads and clear them every time? How can I avoid this error?

Here is my create function from my controller:

Code:
session[:post_params].deep_merge!(params[:post]) if params[:post]
    session[:duration] = params[:post_duration] if params[:post_duration]


    @post = Post.new(session[:post_params])
    @post.current_step = session[:post_step]

   unless @post.valid?
      logger.info("attachment " +  @post.assets.first.attachment.inspect)
      @post.assets.first.attachment.clear
      @post.assets.first.attachment.queued_for_write.clear
    end


    if @post.valid?
      if params[:back_button]
        @post.previous_step
      elsif @post.last_step?
        if @post.all_valid?
          ...
          session[:post_step] = session[:post_params] = nil
          redirect_to @post and return
        end
      else
        @post.next_step
      end  

    session[:post_step] =  @post.current_step
    end

    if @post.new_record?
         render "new"
    end
  end

Thank you for reading.