Uploading Files Into Ruby On Rails ActiveStorage

Introduction

When storing static files in Rails, the first toolsets I reach for are 3rd party gems like: CarrierWave or Paperclip (before they deprecated it in favour of Active Storage). Active Storage was introduced with Rails 5.2. 

Active Storage facilitates uploading files to a cloud storage service like Amazon S3, Google Cloud Storage, or Microsoft Azure Storage and attaching those files to Active Record objects. It comes with a local disk-based service for development and testing and supports mirroring files to subordinate services for backups and migrations.

Using Active Storage, an application can transform image uploads with ImageMagick, generate image representations of non-image uploads like PDFs and videos, and extract metadata from arbitrary files.

In this article, we will focus on how to make the validation of active storage's files by creating a simple app.

Go in the terminal and generate a new app

rails new app

After cd in the app folder crated, let's generate a simple blog app with the scaffold command.

rails g scaffold Post title:string content:text

When the process finished don't forget to migrate

rails db:migrate

We can lunch the server now

rails server

And by visiting the

localhost:3000/posts/index

Let's set the routes to posts/index by editing the

config/routes.rb

#config/routes.rb

Rails.application.routes.draw do
  resources :posts
  root to: 'posts#index'
end

Let's now add the image to our Post with active storage.

Set up

First, we need to install active storage in our project. We will need to run this command on the terminal lines

rails active_storage:install

After running this command, Rails generates a migration for you. Upon inspection of that migration, and creates 2 different tables:

active_storage_blobs 

The next table, 

active_storage_attachments

Don't forget to run the migration command At the end

rails db:migrate

Adding the image to the Model, View and Controller

By visiting our

app/models/post.rb

#app/models/post.rb

class Post < ApplicationRecord
    has_one_attached :image
end

We will again need to add the image in our controller just at the end in the post_params method add the image to the properties of the model.

  
 #app/controller/posts_controller.rb

 def post_params
      params.require(:post).permit(:title, :content, :image)
 end

We will now go in our views and add the image.

In the

app/views/posts/_form.html.erb

#app/views/posts/_form.html.erb

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

Now we need to load the image in the index and show

#app/views/posts/index.html.erb

<% if post.image.attached? %>
    <td><%= image_tag post.image %></td>
<% end %>

#app/views/posts/show.html.erb

<p>
  <% if @post.image.attached? %>
    <%= image_tag @post.image %>
  <% end %>
</p>

And voila, we can add the image to the post. But what if we want to have the image associate to each post?

In this case, we will need to validate our image so that the user can not create a post without an image.

Let's first validate our title and content fields

# app/models/post.rb

class Post < ApplicationRecord
    has_one_attached :image
    validates :title, :content, presence: true
    validates :title, length: {minimum:5, maximum:25}
    validates :content, length: {minimum:10, maximum:50}
end

By editing our

post.rb

Validation with Active Storage

We've now validated our title and content, but we need again to prevent the user to create a post without an image associated with it.

It is very simple, we can do it by adding this one line. But before that, we need first to add the

gem 'active_storage_validations'

bundle install

# app/models/post.rb

validates :image, attached: true, content_type: %i[png jpg jpeg]

We prevent the user to add files of types different from png, jpg and jpeg and we say that the image must be attached to the post. So he can't submit a post without an associated image.

Restart the server to see the changes.

Voila, we reach our goal, now the user can not submit a Post with an empty image.