Active storage is an easy, built-in rails service that provides integration to your local disk and popular services like S3, Azure and Google Cloud.

Make sure you have Rails 5.2 (AT LEAST!) before starting. Run the command:

bin/rails active_storage:install && bin/rails db:migrate

Navigate to config/storage.yml and confirm the yml file replicates this one:

#config/storage.yml

local:
  service: Disk
  root: <%= Rails.root.join("storage") %>

test:
  service: Disk
  root: <%= Rails.root.join("tmp/storage") %>

amazon:
  service: S3
  access_key_id: ""
  secret_access_key: ""
  bucket: ""
  region: "" # e.g. 'us-east-1'

This tutorial, we will be using the disk locally for some image uploads. Double check your development enviorment that we are writing to our local disk:

# config/environments/development.rb

config.active_storage.service = :local

We can now scaffold our Photo resource to create an upload form to test Active Storage!

rails g scaffold Photo description:text 

then run the db migrations

rails db:migrate

The important thing is to add the has_one_attached :image association in the Photo model.

Then add the file_upload element to the scaffolded form:

  <div class="field">
    <%= f.label :image %>
    <%= f.file_field :image %>
  </div>

Also, add the photo to show up in the show.html.erb file

<%= image_tag event.image %>

Finally, add image to the permitted params in the photo controller

def photo_params
 params.require(:photo).permit(:description, :image)
end