Alex F

Hey Mitja, this post is a bit old now but maybe I can help the next person looking for this information :)

The way I've dealt with this exact same situation was with a job (ActiveJob or Sidekiq or whatever you choose to use). On the model that has the photo attachment, I have a callback like this:

after_commit :process_images, if: :photos_attached?

process_images simply calls a job: ProcessImagesJob.perform_later(self)

ProcessImagesJob looks something like this. I removed my app specific code, but hopefully you'll get the idea:

photos.each do |photo|
   next unless photo&.representable?

    preview_variant = photo.representation(resize_to_limit: [300, 300])
    large_variant = photo.representation(resize_to_limit: [1000, 1000])

    preview_variant.processed
    large_variant.processed
end

This generates the variant files on my storage provider, so they're ready to be used when the user views the image. Hope that helps!