Set A Timestamp Field To The Current Time

To set a timestamp field to the current time, you could reach for the #update method like you would when modifying any other field.

MagicLink
  .find_by(token: some_token)
  .update(used_at: Time.zone.now)

This works, but it's more verbose than is necessary and requires that you construct the right timestamp for now (time zones and all).

Rails has a more concise and idomatic way of doing this: #touch.

MagicLink
  .find_by(token: some_token)
  .touch(:used_at)

Updating a timestamp to the current time is a common action in web applications, so Rails offers the #touch method as a shorthand for doing it. This will set the given field, in this case :used_at, to the current time. This will also set the updated_at/on field.