Active Storage

Active Storage makes it simple to upload and reference files in cloud services like Amazon S3, Google Cloud Storage, or Microsoft Azure Storage, and attach those files to Active Records. Supports having one main service and mirrors in other services for redundancy. It also provides a disk service for testing or local deployments, but the focus is on cloud storage.

Files can be uploaded from the server to the cloud or directly from the client to the cloud.

Image files can furthermore be transformed using on-demand variants for quality, aspect ratio, size, or any other MiniMagick supported transformation.

Compared to other storage solutions

A key difference to how Active Storage works compared to other attachment solutions in Rails is through the use of built-in Blob and Attachment models (backed by Active Record). This means existing application models do not need to be modified with additional columns to associate with files. Active Storage uses polymorphic associations via the Attachment join model, which then connects to the actual Blob.

Blob models store attachment metadata (filename, content-type, etc.), and their identifier key in the storage service. Blob models do not store the actual binary data. They are intended to be immutable in spirit. One file, one blob. You can associate the same blob with multiple application models as well. And if you want to do transformations of a given Blob, the idea is that you'll simply create a new one, rather than attempt to mutate the existing one (though of course you can delete the previous version later if you don't need it).

Installation

Run rails active_storage:install to copy over active_storage migrations.

Examples

One attachment:

1class User < ApplicationRecord
2  # Associates an attachment and a blob. When the user is destroyed they are
3  # purged by default (models destroyed, and resource files deleted).
4  has_one_attached :avatar
5end
6
7# Attach an avatar to the user.
8user.avatar.attach(io: File.open("/path/to/face.jpg"), filename: "face.jpg", content_type: "image/jpg")
9
10# Does the user have an avatar?
11user.avatar.attached? # => true
12
13# Synchronously destroy the avatar and actual resource files.
14user.avatar.purge
15
16# Destroy the associated models and actual resource files async, via Active Job.
17user.avatar.purge_later
18
19# Does the user have an avatar?
20user.avatar.attached? # => false
21
22# Generate a permanent URL for the blob that points to the application.
23# Upon access, a redirect to the actual service endpoint is returned.
24# This indirection decouples the public URL from the actual one, and
25# allows for example mirroring attachments in different services for
26# high-availability. The redirection has an HTTP expiration of 5 min.
27url_for(user.avatar)
28
29class AvatarsController < ApplicationController
30  def update
31    # params[:avatar] contains a ActionDispatch::Http::UploadedFile object
32    Current.user.avatar.attach(params.require(:avatar))
33    redirect_to Current.user
34  end
35end

Many attachments:

1class Message < ApplicationRecord
2  has_many_attached :images
3end

1<%= form_with model: @message, local: true do |form| %>
2  <%= form.text_field :title, placeholder: "Title" %><br>
3  <%= form.text_area :content %><br><br>
4
5  <%= form.file_field :images, multiple: true %><br>
6  <%= form.submit %>
7<% end %>

1class MessagesController < ApplicationController
2  def index
3    # Use the built-in with_attached_images scope to avoid N+1
4    @messages = Message.all.with_attached_images
5  end
6
7  def create
8    message = Message.create! params.require(:message).permit(:title, :content)
9    message.images.attach(params[:message][:images])
10    redirect_to message
11  end
12
13  def show
14    @message = Message.find(params[:id])
15  end
16end

Variation of image attachment:

1<%# Hitting the variant URL will lazy transform the original blob and then redirect to its new service location %>
2<%= image_tag user.avatar.variant(resize: "100x100") %>

Direct uploads

Active Storage, with its included JavaScript library, supports uploading directly from the client to the cloud.

Direct upload installation

1. Include activestorage.js in your application's JavaScript bundle.

   Using the asset pipeline:

   1//= require activestorage

   Using the npm package:

   1import * as ActiveStorage from "activestorage"
   2ActiveStorage.start()

2. Annotate file inputs with the direct upload URL.

   1<%= form.file_field :attachments, multiple: true, direct_upload: true %>

3. That's it! Uploads begin upon form submission.

Direct upload JavaScript events

Event name	Event target	Event data (event.detail)	Description
direct-uploads:start	<form>	None	A form containing files for direct upload fields was submitted.
direct-upload:initialize	<input>	{id, file}	Dispatched for every file after form submission.
direct-upload:start	<input>	{id, file}	A direct upload is starting.
direct-upload:before-blob-request	<input>	{id, file, xhr}	Before making a request to your application for direct upload metadata.
direct-upload:before-storage-request	<input>	{id, file, xhr}	Before making a request to store a file.
direct-upload:progress	<input>	{id, file, progress}	As requests to store files progress.
direct-upload:error	<input>	{id, file, error}	An error occurred. An alert will display unless this event is canceled.
direct-upload:end	<input>	{id, file}	A direct upload has ended.
direct-uploads:end	<form>	None	All direct uploads have ended.

License

Active Storage is released under the MIT License.

Support

API documentation is at:

• http://api.rubyonrails.org

Bug reports for the Ruby on Rails project can be filed here:

• https://github.com/rails/rails/issues

Feature requests should be discussed on the rails-core mailing list here:

• https://groups.google.com/forum/?fromgroups#!forum/rubyonrails-core