module ActiveStorage::Attached::Model

def has_one_attached(name, dependent: :purge_later, service: nil, strict_loading: false)


end
has_one_attached :avatar, strict_loading: true
class User < ApplicationRecord

pass the +:strict_loading+ option. You can do:
If you need to enable +strict_loading+ to prevent lazy loading of attachment,

end
has_one_attached :avatar, service: :s3
class User < ActiveRecord::Base

pass the +:service+ option. For instance:
If you need the attachment to use a service which differs from the globally configured one,

(i.e. destroyed) whenever the record is destroyed.
If the +:dependent+ option isn't set, the attachment 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::One

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

User.with_attached_avatar

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 attachment.
There is no column defined on the model side, Active Storage takes

end
has_one_attached :avatar
class User < ApplicationRecord

Specifies the relation between a single attachment and the model. 
def has_one_attached(name, dependent: :purge_later, service: nil, strict_loading: false)
  validate_service_configuration(name, service)
  generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
    # frozen_string_literal: true
    def #{name}
      @active_storage_attached ||= {}
      @active_storage_attached[:#{name}] ||= ActiveStorage::Attached::One.new("#{name}", self)
    end
    def #{name}=(attachable)
      attachment_changes["#{name}"] =
        if attachable.nil?
          ActiveStorage::Attached::Changes::DeleteOne.new("#{name}", self)
        else
          ActiveStorage::Attached::Changes::CreateOne.new("#{name}", self, attachable)
        end
    end
  CODE
  has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record, inverse_of: :record, dependent: :destroy, strict_loading: strict_loading
  has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob, strict_loading: strict_loading
  scope :"with_attached_#{name}", -> { includes("#{name}_attachment": :blob) }
  after_save { attachment_changes[name.to_s]&.save }
  after_commit(on: %i[ create update ]) { attachment_changes.delete(name.to_s).try(:upload) }
  reflection = ActiveRecord::Reflection.create(
    :has_one_attached,
    name,
    nil,
    { dependent: dependent, service_name: service },
    self
  )
  yield reflection if block_given?
  ActiveRecord::Reflection.add_attachment_reflection(self, name, reflection)
end