# File lib/active_storage/attached/one.rb, line 58
def attach(attachable)
  record.public_send("#{name}=", attachable)
  if record.persisted? && !record.changed?
    return if !record.save
  end
  record.public_send("#{name}")
end

Attaches an attachable to the record.

If the record is persisted and unchanged, the attachment is saved to the database immediately. Otherwise, it’ll be saved to the DB when the record is next saved.

person.avatar.attach(params[:avatar]) # ActionDispatch::Http::UploadedFile object
person.avatar.attach(params[:signed_blob_id]) # Signed reference to blob from direct upload
person.avatar.attach(io: File.open("/path/to/face.jpg"), filename: "face.jpg", content_type: "image/jpeg")
person.avatar.attach(avatar_blob) # ActiveStorage::Blob object

# File lib/active_storage/attached/one.rb, line 73
def attached?
  attachment.present?
end

Returns true if an attachment has been made.

class User < ApplicationRecord
  has_one_attached :avatar
end

User.new.avatar.attached? # => false

# File lib/active_storage/attached/one.rb, line 33
def attachment
  change.present? ? change.attachment : record.public_send("#{name}_attachment")
end

Returns the associated attachment record.

You don’t have to call this method to access the attachment’s methods as they are all available at the model level.

# File lib/active_storage/attached/one.rb, line 44
def blank?
  !attached?
end

Returns true if an attachment is not attached.

class User < ApplicationRecord
  has_one_attached :avatar
end

User.new.avatar.blank? # => true

# File lib/active_storage/attached/one.rb, line 25
delegate :detach, to: :detach_one

Deletes the attachment without purging it, leaving its blob in place.

# File lib/active_storage/attached/one.rb, line 13
delegate :purge, to: :purge_one

Directly purges the attachment (i.e. destroys the blob and attachment and deletes the file on the service).

# File lib/active_storage/attached/one.rb, line 19
delegate :purge_later, to: :purge_one

Purges the attachment through the queuing system.