A blob is a record that contains the metadata about a file and a key for where that file resides on the service. Blobs can be created in two ways:
-
Ahead of the file being uploaded server-side to the service, via
create_and_upload!
. A rewindableio
with the file contents must be available at the server for this operation. -
Ahead of the file being directly uploaded client-side to the service, via
create_before_direct_upload!
.
The first option doesn't require any client-side JavaScript integration, and can be used by any other back-end service that deals with files. The second option is faster, since you're not using your own server as a staging point for uploads, and can work with deployments like Heroku that do not provide large amounts of disk space.
Blobs are intended to be immutable in as-so-far as their reference to a specific file goes. You're allowed to update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file. If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one.
- MODULE ActiveRecord
- MODULE ActiveStorage
- MODULE Digest
- CLASS ActiveStorage::Blob