title: Undefined method `image' for #<ActiveStorage::Attachment:
body: <p>I'm trying to implement photo upload using DropzoneJS and Active Storage but at this point, my app throws <code>undefined method 'image' for #&lt;ActiveStorage::Attachment:0x00007fa51201dd80&gt;</code> error.</p>
  <p><a href="https://i.stack.imgur.com/QDq45.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QDq45.jpg" alt="enter image description here" /></a></p>
  <p><strong>models/car.rb</strong></p>
  <p><a href="https://i.stack.imgur.com/cewxm.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cewxm.jpg" alt="enter image description here" /></a></p>
  <p><strong>index.html.erb</strong></p>
  <p><a href="https://i.stack.imgur.com/0YZQX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0YZQX.jpg" alt="enter image description here" /></a></p>
  <p><a href="https://i.stack.imgur.com/eR91L.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eR91L.jpg" alt="enter image description here" /></a></p>
  <p>My Gemfile. Do i need to uncomment image-processing gem to enable and use?</p>
  <pre><code>source 'https://rubygems.org'
  git_source(:github) { |repo| &quot;https://github.com/#{repo}.git&quot; }
  
  ruby '2.6.5'
  
  # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
  gem 'rails', '~&gt; 6.0.0'
  # Use sqlite3 as the database for Active Record
  gem 'sqlite3', '~&gt; 1.4'
  #gem 'pg'
  # Use Puma as the app server
  gem 'puma', '~&gt; 3.11'
  # Use SCSS for stylesheets
  gem 'sass-rails', '~&gt; 5'
  # Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
  gem 'webpacker', '~&gt; 4.0'
  # Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
  gem 'turbolinks', '~&gt; 5'
  # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
  gem 'jbuilder', '~&gt; 2.7'
  # Use Redis adapter to run Action Cable in production
  # gem 'redis', '~&gt; 4.0'
  # Use Active Model has_secure_password
  # gem 'bcrypt', '~&gt; 3.1.7'
  
  # Use Active Storage variant
  # gem 'image_processing', '~&gt; 1.2'
  
  # Reduces boot times through caching; required in config/boot.rb
  gem 'bootsnap', '&gt;= 1.4.2', require: false
  
  group :development, :test do
    # Call 'byebug' anywhere in the code to stop execution and get a debugger console
    gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
  end
  
  group :development do
    # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
    gem 'web-console', '&gt;= 3.3.0'
    gem 'listen', '&gt;= 3.0.5', '&lt; 3.2'
    # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
    gem 'spring'
    gem 'spring-watcher-listen', '~&gt; 2.0.0'
    #Provides better error page for Rails and other Rack apss.
    gem 'better_errors', '~&gt; 2.5', '&gt;= 2.5.1'
  end
  
  group :test do
    # Adds support for Capybara system testing and selenium driver
    gem 'capybara', '&gt;= 2.15'
    gem 'selenium-webdriver'
    # Easy installation and use of web drivers to run system tests with browsers
    gem 'webdrivers'
  end
  
  # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
  gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
  
  gem 'bootstrap', '~&gt; 4.4.1'
  
  gem 'devise', '~&gt; 4.7', '&gt;= 4.7.1'
  gem 'jquery-rails'
  
  gem 'omniauth', '~&gt; 1.9'
  
  gem 'omniauth-facebook', '~&gt; 5.0'
  
  #new gems
  group :development, :production do
    gem 'capistrano', '~&gt; 3.11', require: false
    gem 'capistrano-bundler', require: false
    gem 'capistrano-rails', '~&gt; 1.4', require: false
    gem 'capistrano-passenger', '~&gt; 0.2.0'
    gem 'capistrano-rbenv', '~&gt; 2.1', '&gt;= 2.1.4', github: 'capistrano/rbenv', require: false
  end
  #gem 'capistrano', '~&gt; 3.11'
  #gem 'capistrano-rails', '~&gt; 1.4'
  #gem 'capistrano-passenger', '~&gt; 0.2.0'
  #gem 'capistrano-rbenv', '~&gt; 2.1', '&gt;= 2.1.4'
  
  gem 'jquery-ui-rails', '~&gt; 5.0'
  </code></pre>
  <p>This is a bit confusing as i'm new to this.</p>
  <p>Am i suppose to create a Controller for <code>Photos</code>?</p>
  <p>Do i need to add a certain gem too?</p>
  <p>How do i fix this?</p>