module ActiveStorage::Attached::Model

def has_many_attached(name, dependent: :purge_later)

(i.e. destroyed) whenever the record is destroyed.
If the +:dependent+ option isn't set, all the attachments will be purged

proxy that provides the dynamic proxy to the associations and factory methods, like +#attach+.
The system has been designed to having you go through the ActiveStorage::Attached::Many

most circumstances.
and +photos_blobs+. But you shouldn't need to work with these associations directly in
ActiveStorage::Blob record. These associations are available as +photos_attachments+
ActiveStorage::Attachment record and a +has_many-through+ association to a
Under the covers, this relationship is implemented as a +has_many+ association to a

Gallery.where(user: Current.user).with_attached_photos

To avoid N+1 queries, you can include the attached blobs in your query like so:

care of the mapping between your records and the attachments.
There are no columns defined on the model side, Active Storage takes

end
has_many_attached :photos
class Gallery < ActiveRecord::Base

Specifies the relation between multiple attachments and the model. 
def has_many_attached(name, dependent: :purge_later)
  generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
    def #{name}
      @active_storage_attached_#{name} ||= ActiveStorage::Attached::Many.new("#{name}", self)
    end
    def #{name}=(attachables)
      if ActiveStorage.replace_on_assign_to_many
        attachment_changes["#{name}"] =
          if Array(attachables).none?
            ActiveStorage::Attached::Changes::DeleteMany.new("#{name}", self)
          else
            ActiveStorage::Attached::Changes::CreateMany.new("#{name}", self, attachables)
          end
      else
        if Array(attachables).any?
          attachment_changes["#{name}"] =
            ActiveStorage::Attached::Changes::CreateMany.new("#{name}", self, #{name}.blobs + attachables)
        end
      end
    end
  CODE
  has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment", inverse_of: :record, dependent: :destroy do
    def purge
      each(&:purge)
      reset
    end
    def purge_later
      each(&:purge_later)
      reset
    end
  end
  has_many :"#{name}_blobs", through: :"#{name}_attachments", class_name: "ActiveStorage::Blob", source: :blob
  scope :"with_attached_#{name}", -> { includes("#{name}_attachments": :blob) }
  after_save { attachment_changes[name.to_s]&.save }
  after_commit(on: %i[ create update ]) { attachment_changes.delete(name.to_s).try(:upload) }
  ActiveRecord::Reflection.add_attachment_reflection(
    self,
    name,
    ActiveRecord::Reflection.create(:has_many_attached, name, nil, { dependent: dependent }, self)
  )
end