method

has_one_attached

v5.2.3 - Show latest stable - 0 notes - Class: Macros

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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/macros.rb, line 30
    def has_one_attached(name, dependent: :purge_later)
      class_eval         def #{name}          @active_storage_attached_#{name} ||= ActiveStorage::Attached::One.new("#{name}", self, dependent: #{dependent == :purge_later ? ":purge_later" : "false"})        end        def #{name}=(attachable)          #{name}.attach(attachable)        end, __FILE__, __LINE__ + 1

      has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record, inverse_of: :record, dependent: false
      has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob

      scope :"with_attached_#{name}", -> { includes("#{name}_attachment": :blob) }

      if dependent == :purge_later
        after_destroy_commit { public_send(name).purge_later }
      else
        before_destroy { public_send(name).detach }
      end
    end

has_one_attached

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