Using a join model to annotate Active Storage blobs with custom data

add_images.rb

Project.first.images.attach(io: File.open(filename), filename: filename, content_type: 'image/jpg')

image.rb

class Image < ApplicationRecord
  belongs_to :project

  has_one_attached :file
  delegate_missing_to :file

  scope :positioned, -> { order(position: :asc) }
end

index.html.erb

<% @projects.with_attached_images.each do |project| %>
  <%# ... %>
<% end %>

project.rb

class Project < ApplicationRecord
  has_many :images, dependent: :destroy
  scope :with_attached_images, -> { includes(:images).merge(Image.with_attached_file) }
end

show.html.erb

<% @project.images.positioned.with_attached_file.each do |image| %>
  <%= image_tag image %>
<% end %>