不能。对于has_one_attached，has_many_attached宏，此时只有一个可能的选项，即:dependent。https://github.com/rails/rails/blob/master/activestorage/lib/active_storage/attached/macros.rb#L30
看（也许你有下投的原因，但它是关于“直接”上传所以...）：How to specify a prefix when uploading to S3 using activestorage's direct upload?。响应来自Active Storage的主要维护者。

使用before_validation钩子在S3上设置所需的密钥，并在S3上设置内容处置对象属性所需的文件名。
附件模型上的key和filename属性将传递到ActiveStorage S3 gem，并转换为S3密钥+内容处置对象属性。

class MyCoolItem < ApplicationRecord
  has_one_attached :preview_image
  has_one_attached :download_asset

  before_validation :set_correct_attachment_filenames

  def preview_image_path
    # This key has to be unique across all assets. Fingerprint it yourself.
    "/previews/#{item_id}/your/unique/path/on/s3.jpg"
  end

  def download_asset_path
    # This key has to be unique across all assets. Fingerprint it yourself.
    "/downloads/#{item_id}/your/unique/path/on/s3.jpg"
  end
  
  def download_asset_filename
    "my-friendly-filename-#{item_id}.jpg"
  end

  def set_correct_attachment_filenames
    # Set the location on S3 for new uploads:
    preview_image.key = preview_image_path if preview_image.new_record?
    download_asset.key = download_asset_path if download_asset.new_record?

    # Set the content disposition header of the object on S3:
    download_asset.filename = download_asset_filename if download_asset.new_record?
  end
end