Rails and Active Storage, how to assign attachment directly on the create call?

I have MyModel with:

has_one_attached :video

I see I can do this:

my_model = MyModel.create!()
my_model.video.attach(io: File.open("path/my_video.webm"), filename: "video.webm")

And it works properly.

But I am wondering if there is a way of doing the attachment assignation into the create() call like:

MyModel.create!(
  video: File.read("path/my_video.webm")
)

If I do the above I see this error:

/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/activesupport-6.1.4.1/lib/active_support/message_verifier.rb:176:in `verify': ActiveSupport::MessageVerifier::InvalidSignature (ActiveSupport::MessageVerifier::InvalidSignature)

I've tried this:

MyModel.create!(
  video: File.open("path/my_video.webm")
)

I am get this error:

/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/activestorage-6.1.4.1/lib/active_storage/attached/changes/create_one.rb:74:in `find_or_build_blob': Could not find or build blob: expected attachable, got #File:/Users/fernando.guillen/Development/PlaycocolaBackend/test/fixtures/files/video.webm (ArgumentError)

Solution

You can do it by creating an instance of ActionDispatch::Http::UploadedFile. This is basically just a wrapper around a tempfile instance which Rails uses internally when dealing with file uploads.

MyModel.create!(
  video: ActionDispatch::Http::UploadedFile.new(
    tempfile: File.open("path/my_video.webm"), 
    filename: "video.webm",
    content_type: 'video/webm'
  )
)

In terms of efficiency or LOC it doesn't really have any advantages over calling .attach. It is a nifty trick though for dealing with files passed as base64 encoded strings in JSON.