Rails — Serializing Active Storage uploads with Active Model

How to serialize files uploaded with Active Storage to JSON, then upload the files via an AJAX request.

This is a short guide for Rails applications that utilize Active Storage to handle file uploads. I won’t detail that process — there’s already a recent and well-written blog on the topic that also outlines how to store the images with GCS or AWS and deploy to Heroku.

The first piece is relatively straightforward. I used Active Model to serialize data. rails g wine serializer generates a directory for serializers, and creates a serializer for the wine class.

class WineSerializer < ActiveModel::Serializer
end

From there, I added in the attributes and relationships I wanted to serialize.

class WineSerializer < ActiveModel::Serializer
  attributes :id, :producer, :wine_name, :wine_type, :price_range, :vintage,
             :rating, :notes, :favorite
						 
  belongs_to :user
  belongs_to :varietal
  belongs_to :country
end

The last step is adding the Rails URL helpers, and creating a method to make the image an attribute.

class WineSerializer < ActiveModel::Serializer
  include Rails.application.routes.url_helpers