method

has_one_attached

v6.1.7.7 - Show latest stable - 0 notes - Class: Model

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What's this?

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

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.

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

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

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

Show source

# File activestorage/lib/active_storage/attached/model.rb, line 50
      def has_one_attached(name, dependent: :purge_later, service: nil, strict_loading: false)
        validate_service_configuration(name, service)

        generated_association_methods.class_eval           # 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, __FILE__, __LINE__ + 1

        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: %[ 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
        )
        ActiveRecord::Reflection.add_attachment_reflection(self, name, reflection)
      end

has_one_attached

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