# Active Storage in Rails
## Overview

Active Storage is a new feature of Ruby on Rails 5.2. Active Storage allows Rails developers to manage file uploads, cloud storage, and document management tied to models throughout apps. It attaches pointers to the Active Record object and will upload it asynchronously.

:::info
Rails 5.2 and later: Active Storage included
Rails 5.1.6 and older: requires `gem`
:::

## Some Features
### Mirror Service
Allows syncing of files between multiple cloud storage services.

For example, in `config/storage.yml` we have this block:

development:
  service: Mirror
  primary: amazon
  mirrors:
    - azure
    - google

In this example, the mirror service would first upload files to **Amazon** since it is set as the primary. Then, it would push the same files to **Azure** and **Google Cloud**. File removal takes place in the same order. This can be helpful when switching between cloud services or when creating backups.

### Direct Uploads
Since Active Storage comes with a Javascript library (`activestorage.js`) we can upload files from the front end of our site to cloud storage directly.

Some events used by this library are:

direct-upload:start
direct-upload:initialize
direct-upload:progress

### Asynchronous Upload
Doesn’t require adding any background job to upload files asynchronously. It uses Active Job to upload files to the cloud.

## Installation

1. Within your Rails app, look in the following folders:

`config/environments/development` and `config/environments/production`

Ensure the following is included: `config.active_storage.service = :local`. This tells the app to save your uploads locally.

2. To install into your application run:

rails active_storage:install

This generates an `active_storage_blobs` and an `active_storage_attachments` table.

Run:

rails db:migrate

Once you configure it you can go to your models, and define your attachments. If you have a model for User and need to upload the profile picture of that user and allow them to upload other files:

class User < ApplicationRecord
    has_one_attached :profile_picture
    has_many_attached :uploads
end

The `has_one_attached` method maps a one to one relationship between the Active Record Object and the uploaded file. The `has_many_attached` maps a one to many relationship.

When you have a form for the user using form_with you can simply add fields for the attachments within that form:

<%= form.file_field :profile_picture %>
<%= form.file_field :uploads, multiple: true %>

We also have to create an action in the user controller that takes in the user params, here we just added :profile_picture and :uploads into it:

def create
  @user = User.create(user_params)
end

private

def user_params
  params.require(:user).permit(:email, :password, :profile_picture, uploads: [])
end

*Notice uploads parameter has many so we use array notation here.

One cool thing about this, is that if you go to the index page that might list the users, all you have to do to display an image is say `<%= image_tag @user.profile_picture %> `

## Demo

## Additional Resources

* [Active Storage Overview](https://guides.rubyonrails.org/active_storage_overview.html)
* [Active Storage README](https://github.com/rails/rails/blob/d3893ec38ec61282c2598b01a298124356d6b35a/activestorage/README.md)
* [DEANOUT on YouTube: Active Storage Tutorial Series](https://www.youtube.com/channel/UCRQv-3VvPT9mArF5RfrlpKQ)
* [Tutorial on how to use Active Storage on Rails 5.2](https://www.engineyard.com/blog/active-storage)