instance method `has_one_attached`

Ruby on Rails 7.2.3

Since v6.0.6

Available in: v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

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

Specifies the relation between a single attachment and the model.

class User < ApplicationRecord
  has_one_attached :avatar
end

There is no column defined on the model side, Active Storage takes care of the mapping between your records and the attachment.

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

User.with_attached_avatar

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

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

The :dependent option defaults to :purge_later. This means the attachment will be purged (i.e. destroyed) in the background whenever the record is destroyed. If an ActiveJob::Backend queue adapter is not set in the application set it to purge instead.

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

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

:service can also be specified as a proc, and it will be called with the model instance:

class User < ActiveRecord::Base
  has_one_attached :avatar, service: ->(user) { user.in_europe_region? ? :s3_europe : :s3_usa }
end

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

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

Note: Active Storage relies on polymorphic associations, which in turn store class names in the database. When renaming classes that use has_one_attached, make sure to also update the class names in the active_storage_attachments.record_type polymorphic type column of the corresponding rows.

Parameters

name req
dependent key = :purge_later
service key = nil
strict_loading key = false

Source

# File activestorage/lib/active_storage/attached/model.rb, line 106
      def has_one_attached(name, dependent: :purge_later, service: nil, strict_loading: false)
        Attached::Model.validate_service_configuration(service, self, name) unless service.is_a?(Proc)

        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? || attachable == ""
                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}", -> {
          if ActiveStorage.track_variants
            includes("#{name}_attachment": { blob: {
              variant_records: { image_attachment: :blob },
              preview_image_attachment: { blob: { variant_records: { image_attachment: :blob } } }
            } })
          else
            includes("#{name}_attachment": :blob)
          end
        }

        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

Defined in activestorage/lib/active_storage/attached/model.rb line 106 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveStorage::Attached::Model

Signature

Parameters