instance method `has_one_attached`

Ruby on Rails 6.0.6

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)

Specifies the relation between a single attachment and the model.

class User < ActiveRecord::Base
  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.

If the :dependent option isn’t set, the attachment will be purged (i.e. destroyed) whenever the record is destroyed.

Parameters

name req
dependent key = :purge_later

Source

# File activestorage/lib/active_storage/attached/model.rb, line 33
      def has_one_attached(name, dependent: :purge_later)
        generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
          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
        has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob

        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) }

        ActiveRecord::Reflection.add_attachment_reflection(
          self,
          name,
          ActiveRecord::Reflection.create(:has_one_attached, name, nil, { dependent: dependent }, self)
        )
      end

Defined in activestorage/lib/active_storage/attached/model.rb line 33 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveStorage::Attached::Model

Signature

Parameters