Activestorage: get S3 key (not Rails blob key)

Question

I'm using Activestorage. I want to retrieve the S3 key to hand off to a microservice. I don't want to download the blob or anything like that in the Rails app, I just want to provide the file path/key in an API request.

service_url is overkill because I already have access the bucket in the microservice, not to mention the fact that these are large files and I don't need to transfer them unnecessarily.

What are my options?

Answer 1

Using service_url is not only overkill, it also runs into issues if you try to use it outside of the ActiveStorage controller, as described here.

Better is ActiveStorage#key, which for S3 will return just the S3 key to your object. It is still not what you're supposed to use for public values - ActiveStorage#signed_id gives you the railsy key. But if you want the raw S3 key (as I did for a service API), key works and doesn't complain outside of the controller.

So in your case:

def logo_key_on_s3
  logo.key
end

should work.