Support for CarrierWave::SanitizedFile and CarrierWave::Storage::Fog::File

[Martin Liptak]

I'm generating PDFs with a background image uploaded with Carrierwave. Carrierwave pseudo IO object is either CarrierWave::SanitizedFile (in development) or CarrierWave::Storage::Fog::File (in production). Both of them have read method, but they don't support rewind (and they can be read multiple times, it's always from the beginning). I checked Prawn code and discovered that it could be easily made more universal (possibly support other objects acting IO-like without rewind).

def verify_and_open_image(io_or_path)
  # File or IO
  if io_or_path.respond_to?(:rewind)
    io = io_or_path
    # Rewind if the object we're passed is an IO, so that multiple embeds of
    # the same IO object will work
    io.rewind
    # read the file as binary so the size is calculated correctly
    # guard binmode because some objects acting io-like don't implement it
    io.binmode if io.respond_to?(:binmode)
    return io
  end
  # String or Pathname
  io_or_path = Pathname.new(io_or_path)
  fail ArgumentError, "#{io_or_path} not found" unless io_or_path.file?
  io = io_or_path.open('rb')
  io
end

The only method required after verify_and_open_image is read, but verify_and_open_image checks for rewind.

io = verify_and_open_image(file)
image_content = io.read

How about checking for the read method in verify_and_open_image and making io.rewind optional, as io.binmode?

def verify_and_open_image(io_or_path)
  if io_or_path.respond_to?(:read)
    io = io_or_path
   
    # Rewind if the object we're passed is an IO, so that multiple embeds of
    # the same IO object will work
    # Guard rewind because some objects acting io-like don't implement it
    io.rewind if io.respond_to?(:rewind)


    # Read the file as binary so the size is calculated correctly
    # Guard binmode because some objects acting io-like don't implement it
    io.binmode if io.respond_to?(:binmode)
   
    io
  else
    path = Pathname.new(io_or_path)
    fail ArgumentError, "#{path} not found" unless path.file?
    io = path.open('rb')
   
    io
  end
end

I was able to work around the issue in my code like this

require "open-uri"

def prawn_image
  if Rails.env.production?
    open(model.uploader_url)
  else
    model.uploader.current_path
  end
end

With the rewind guard it could look like this

def prawn_image
  model.uploader.file
end

What do you think?

[Alexander Mankuta]

Hello Martin,

We generally leave Prawn integration with third-party gems to the user. That is you, in this case.

You can easily simulate IO by passing StringIO.new(uploaded_file.read) to Prawn instead of CarrierWave objects..

--
Regards,
Alex

[Martin Liptak]

Thanks, StringIO solved my issue.