method

has_one_attached

v6.0.0 - Show latest stable - 0 notes - Class: Model

1.0.0
1.1.6
1.2.6
2.0.3
2.1.0
2.2.1
2.3.8
3.0.0
3.0.9
3.1.0
3.2.1
3.2.8
3.2.13
4.0.2
4.1.8
4.2.1
4.2.7
4.2.9
5.0.0.1
5.1.7
5.2.3
6.0.0 (0)
6.1.3.1 (38)
6.1.7.7 (0)
7.0.0 (0)
7.1.3.2 (0)
7.1.3.4 (0)
What's this?

has_one_attached(name, dependent: :purge_later) public

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.

Show source

# File activestorage/lib/active_storage/attached/model.rb, line 33
      def has_one_attached(name, dependent: :purge_later)
        generated_association_methods.class_eval           def #{name}            @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, __FILE__, __LINE__ + 1

        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: %[ 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

has_one_attached

Related methods