_form.html.haml

  %dl
    %dt=label :file, I18n.t("activerecord.attributes.app.file_label")
    %dd
      =f.file_field :file
      %small.block=form_field_message("app", "file", @version.errors[:file])

  %dl
    %dt=label :signature, I18n.t("activerecord.attributes.app.file_label")
    %dd
      =f.file_field :signature
      %small.block=form_field_message("app", "signature", @version.errors[:signature])

  =f.hidden_field :file_cache
  =f.hidden_field :signature_cache

error

No such file or directory - /home/daniel/code/work/walk-manager-3/tmp/uploads/1403273353.829841.945.639/test1.posxml.pem

file_uploader.rb

class FileUploader < CarrierWave::Uploader::Base

  # Include RMagick or ImageScience support:
  # include CarrierWave::RMagick
  # include CarrierWave::ImageScience

  # Choose what kind of storage to use for this uploader:
  storage = :file

  if Rails.env.test? or Rails.env.cucumber?
    CarrierWave.configure do |config|
      config.enable_processing = false
    end
  end

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "#{Rails.root}/tmp/uploads/#{DateTime.now.to_f}.#{rand(999)}.#{rand(999)}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  #   process :scale => [50, 50]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  def extension_white_list
    %w(wsxml)
  end

  # Override the filename of the uploaded files:
  # def filename
  #   "something.jpg" if original_filename
  # end
end

gems

carrierwave-0.9.0
rails-3.2.16
ruby 2.0.0p481

signature_uploader.rb

class SignatureUploader < CarrierWave::Uploader::Base

  # Include RMagick or ImageScience support:
  # include CarrierWave::RMagick
  # include CarrierWave::ImageScience

  # Choose what kind of storage to use for this uploader:
  storage = :file

  if Rails.env.test? or Rails.env.cucumber?
    CarrierWave.configure do |config|
      config.enable_processing = false
    end
  end

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "#{Rails.root}/tmp/uploads/#{DateTime.now.to_f}.#{rand(999)}.#{rand(999)}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  #   process :scale => [50, 50]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  def extension_white_list
    %w(pem)
  end

  # Override the filename of the uploaded files:
  # def filename
  #   "something.jpg" if original_filename
  # end
end

version.rb

class Version < ActiveRecord::Base
  # ...
  mount_uploader :file, FileUploader
  mount_uploader :signature, SignatureUploader
  # ...
end