ActiveStorage in Rails 6 and 7 does not support to upload files in background which in most cases delays the submit process and then makes the visitor get bored or receive a timeout error.
This is a Ruby on Rails gem to upload activestorage files in background by saving them as base64 encoded in the database (important for apps hosted in kubernetes) and be processed later.

• Upload files in background
• Ability to add new files instead of replacing the old ones when using using has_many_attached
• Ability to upload files with the original filename or a custom one
• Ability to preprocess the files before uploading them (Rails 7+)
  Note: This gem assumes that the app has already configured activestorage.

• Add this line to your application's Gemfile:

    gem 'activestorage-delayed', '>= 0.1.3'

• And then execute: bundle install
• Generate the migration: rails g migration add_activestorage_delayed
• Add the following content to the migration file:

    create_table :activestorage_delayed_uploads do |t|
      t.references :uploadable, polymorphic: true, null: false
      t.string :attr_name, null: false
      t.string :deleted_ids, default: ''
      t.boolean :clean_before, default: false
      t.text :files
      t.timestamps
    end

• Run the migration: rails db:migrate

• Include ActivestorageDelayed::DelayedConcern
• Add delayed_attach to the files you want to upload in background

  class User < ApplicationRecord
  include ActivestorageDelayed::DelayedConcern

  has_one_attached :photo, required: true, use_filename: true, variant_info: { resize_to_fit: [400, 400], convert: 'jpg' }
  delayed_attach :photo

  has_many_attached :certificates
  delayed_attach :certificates
end

• required: If set to true, the photo or the photo_tmp will be required before saving.
• use_filename: If set to true, the image filename will be used as the name of uploaded file instead of the hash-key used by activestorage
• variant_info: (Hash) Variant information to be performed before uploading the file.

• Upload a single file

    User.create(photo_tmp: File.open('my_file.png')) # uploads the file in background
    User.create(photo: File.open('my_file.png')) # uploads the file directly

  HTML:

  f.file_field :photo_tmp

• Upload multiple files

    User.create(certificates_tmp: [File.open('my_file.png'), File.open('my_file.png')])

  HTML:

  = f.file_field :certificates_tmp, multiple: true

• Deletes first 2 certificates and uploads a new one

    file_ids = User.first.certificates.limit(2).pluck(:id)
    User.first.update(certificates_tmp: { deleted_ids: file_ids, files: [File.open('my_file.png')] })

  HTML

  = file_field_tag 'user[certificates_tmp][files][]', multiple: true
  - user.certificates.each do |file|
    %li
      = image_tag(file)
      = check_box_tag 'user[certificates_tmp][deleted_ids][]', value: file.id

• Removes all certificates before uploading a new one

    User.first.update(certificates_tmp: { clean_before: true, files: [File.open('my_file.png')] })

• Upload files with custom names (requires use_filename: true): <attr_name>_filename

  class User < ApplicationRecord
    def photo_filename(filename)
      "#{id}-#{full_name.parameterize}#{File.extname(filename)}"
    end
  end

  When <attr_name>_filename is defined, then it is called to fetch the uploaded file name.
  Note: Check this if you want to rename an already uploaded file (remote file)

• Capture event when file upload has failed: <attr_name>_error_upload

    class User < ApplicationRecord
      # @param error [StandardError]
      # @param file_data [Hash<'filename'>]
      def photo_error_upload(error, file_data)
        puts "Failed uploading photo #{file_data['filename']}: #{error.message}"
      end
    end

• Capture event when file has been uploaded: <attr_name>_after_upload

    class User < ApplicationRecord
      # @param file_data [Hash<'filename'>]
      def photo_after_upload(file_data)
        puts "Photo #{file_data['filename']} has been uploaded"
      end
  
      def photo_after_upload_all
        puts "All photos have been uploaded"
      end
    end

Note:
<attr_name>_delayed_uploads is a has_many association that contains the list of scheduled uploads for the corresponding attribute.

Bug reports and pull requests are welcome on https://github.com/owen2345/activestorage-delayed. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

To ensure your contribution changes, run the tests with: docker-compose run test

The gem is available as open source under the terms of the MIT License.