File attachment and handling validation errors with Rails and Paperclip

Question

I have a form to send a message with attachments.

• User select files to attach
• Press submit and wait (long time) until all the file are uploaded
• The user forgot to type the message so the validation failed
• The user need to upload all the files again (long time)

Is there a simple way to make rails to remember the already uploaded files? (I have been using paperclip)

Answer 1

One way would be to create the Message object initially with default (passing) values when you start uploading the file and then just issue a PUT request to update the message object using the form.

This way, the Message object is valid upon creation and the only thing you're validating is that the update information is valid as well (if it's not, the message will just have the default value and the user won't have to re-upload the file).

You can set up the database attribute (via a Rails migration) to have a set default value so you don't have to do this in the controller.

change_column_default(:messages, :content, "You have a new message!")

Answer 2

I had to fix this on a recent project using PaperClip. It's a bit hacky but it works. I've tried calling cache_images() using after_validation and before_save in the model but it fails on create for some reason that I can't determine so I just call it from the controller instead. Hopefully this saves someone else some time!

model:

class Shop < ActiveRecord::Base    
  attr_accessor :logo_cache

  has_attached_file :logo

  def cache_images
    if logo.staged?
      if invalid?
        FileUtils.cp(logo.queued_for_write[:original].path, logo.path(:original))
        @logo_cache = encrypt(logo.path(:original))
      end
    else
      if @logo_cache.present?
        File.open(decrypt(@logo_cache)) {|f| assign_attributes(logo: f)}
      end
    end
  end

  private

  def decrypt(data)
    return '' unless data.present?
    cipher = build_cipher(:decrypt, 'mypassword')
    cipher.update(Base64.urlsafe_decode64(data).unpack('m')[0]) + cipher.final
  end

  def encrypt(data)
    return '' unless data.present?
    cipher = build_cipher(:encrypt, 'mypassword')
    Base64.urlsafe_encode64([cipher.update(data) + cipher.final].pack('m'))
  end

  def build_cipher(type, password)
    cipher = OpenSSL::Cipher::Cipher.new('DES-EDE3-CBC').send(type)
    cipher.pkcs5_keyivgen(password)
    cipher
  end

end

controller:

def create
  @shop = Shop.new(shop_params)
  @shop.user = current_user
  @shop.cache_images

  if @shop.save
    redirect_to account_path, notice: 'Shop created!'
  else
    render :new
  end
end

def update
  @shop = current_user.shop
  @shop.assign_attributes(shop_params)
  @shop.cache_images

  if @shop.save
    redirect_to account_path, notice: 'Shop updated.'
  else
    render :edit
  end
end

view:

= f.file_field :logo
= f.hidden_field :logo_cache

- if @shop.logo.file?
  %img{src: @shop.logo.url, alt: ''}