module ActiveStorage::Blob::Representable

ActiveStorage::Blob#variable?.
transform the blob. To determine whether a blob is variable, call
Raises ActiveStorage::InvariableError if the variant processor cannot

can then produce on-demand.
This will create a URL for that specific blob with that specific variant, which the ActiveStorage::RepresentationsController

<%= image_tag Current.user.avatar.variant(resize_to_limit: [100, 100]) %>

specific variant that can be created by a controller on-demand. Like so:
Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a

Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
This will create and process a variant of the avatar blob that's constrained to a height and width of 100px.

avatar.variant(resize_to_limit: [100, 100]).processed.url

This is only relevant for image files, and it allows any image to be transformed for size, colors, and the like. Example:
Returns an ActiveStorage::Variant or ActiveStorage::VariantWithRecord instance with the set of +transformations+ provided.

def variant(transformations)
  if variable?
    variant_class.new(self, ActiveStorage::Variation.wrap(transformations).default_to(default_variant_transformations))
  else
    raise ActiveStorage::InvariableError
  end
end