How to specify a prefix when uploading to S3 using activestorage's direct upload?

Question

With a standard S3 configuration:

AWS_ACCESS_KEY_ID:        [AWS ID]
AWS_BUCKET:               [bucket name]
AWS_REGION:               [region]
AWS_SECRET_AC         


        

Answer 1

Thank you, Sonia, for your answer.

I tried your solution and it works great, but I encountered problems with overwriting attachments. I often got IntegrityError while doing it. I think, that this and checksum handling may be the reason why the Rails core team don't want to add passing pathname feature. It would require changing the entire logic of the upload method.

ActiveStorage::Attached#create_from_blob method, could also accepts an ActiveStorage::Blob object. So I tried a different approach:

1. Create a Blob manually with a key that represents desired file structure and uploaded attachment.
2. Attach created Blob with the ActiveStorage method.

In my usage, the solution was something like that:

def attach file # method for attaching in the model
  blob_key = destination_pathname(file)
  blob = ActiveStorage::Blob.find_by(key: blob_key.to_s)

  unless blob
    blob = ActiveStorage::Blob.new.tap do |blob|
      blob.filename = blob_key.basename.to_s
      blob.key = blob_key
      blob.upload file
      blob.save!
    end
  end

  # Attach method from ActiveStorage
  self.file.attach blob
end

Thanks to passing a full pathname to Blob's key I received desired file structure on a server.