How to Upload Files in Ruby on Rails?

Uploading files in a web application is a common requirement, whether it's for user profile pictures, documents, or any other files. Ruby on Rails makes this task straightforward with its built-in tools. In this article, we'll walk through the steps to set up file uploads in a Rails app, from creating the project to displaying and downloading the uploaded files.

Prerequisites

1. Ruby on Rails: Understanding of Rails models, controllers, views, and the MVC (Model-View-Controller) architecture. If Ruby on Rails is not already installed, Install Ruby on Rails on Windows or Linux or Install Ruby on Rails on macOS.
2. Active Storage: Familiarity with Rails' Active Storage framework for handling file uploads and attachments.
3. Forms Basics: Knowledge of how to create and process forms in Rails.
4. Routing: Basic understanding of how routing works in Rails, especially how actions like new and create are mapped to URLs.
5. Database Basics: Understanding of how Rails interacts with databases, including how models correspond to database tables.

Approach

In this example, we are using the direct form submission method to upload a file in a Ruby on Rails application.

1. The form is created using the 'form_with' helper, where users can enter a title and select a file to upload.
2. When the form is submitted, the file and title are sent to the server as part of the form data.

This method is straightforward to implement, especially for simple file upload needs. Other methods, such as AJAX file upload, chunked file upload, and direct-to-cloud storage upload, offer more advanced features like asynchronous uploading, handling large files, and offloading storage to cloud services. These approaches can be implemented to enhance user experience and scalability.

Steps to Upload a File

Step 1: Create a Rails App

First, you'll need to create a new Rails application. Open your terminal and run the below command,

rails new file_app

Step 2: Create a Model

To upload files, you'll need a model to store the file information. Let's create a model called 'Folder'. Make sure you are inside your project directory while executing the command.

rails generate model Folder title:string file:string

Here, the title will be a string to store the document's name, and the file will hold the uploaded file's path.

After running the command, migrate the database.

rails db:migrate

Step 3: Use Active Storage

Rails has a built-in tool called Active Storage that makes file uploads easy. There are other useful gems and tools for file handling like,

1. Shrine
2. Carrierwave
3. Dragonfly
4. Paperclip
5. Refile

Active Storage is widely used and recommended. Install Active Storage by running,

rails active_storage:install rails db:migrate

This will add tables to your database to store file uploads.

Step 4: Set Up the Model to Use Active Storage

Now, update the 'Folder' model to attach files using Active Storage. Open 'app/models/folder.rb' and modify it like this,

This line indicates that each instance of the 'Folder' model can have one file attached to it.

Step 5: Create a Form to Upload Files

Next, create a form in your FoldersController to allow users to upload files. Generate the controller using,

rails generate controller Folders

Now, add a 'new' action in 'app/controllers/folders_controller.rb'. This initializes a new, unsaved instance of the 'Folder' model and assigns it to the instance variable @folder.

In the same controller, add a 'create' action to save the uploaded file. The create action in the controller initializes a new 'Folder' with user-submitted parameters, attempts to save it, and either redirects to the document's show page with a success message or re-renders the new form if saving fails. The 'folder_params' method ensures that only permitted parameters are used.

class FoldersController < ApplicationController
    def new
        @folder = Folder.new
    end

    def create
        @folder = Folder.new(folder_params)
      
        if @folder.save
          redirect_to @folder, notice: 'File was successfully uploaded.'
        else
          render :new
        end
    end
      
    private
      
    def folder_params
      params.require(:folder).permit(:title, :file)
    end
end

Step 6: Create the View

Now, create a view to render the upload form. In 'app/views/folders/new.html.erb', add the following code,

<h1>Upload a New File</h1>

<%= form_with(model: @folder, local: true) do |form| %>
  <div class="field">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

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

  <div class="actions">
    <%= form.submit 'Upload' %>
  </div>
<% end %>

Step 7: Display Uploaded Files

To display the uploaded files, add a 'show' action in 'app/controllers/folders_controller.rb',

def show
  @folder = Folder.find(params[:id])
end

Then, create a view to show the document in 'app/views/folders/show.html.erb',

<h1><%= @folder.title %></h1>

<p>
  <%= link_to 'Download file', rails_blob_path(@folder.file, disposition: "attachment") %>
</p>

Step 8: Add Routes

Finally, make sure to add routes for the new actions. In 'config/routes.rb', add: the following,

Rails.application.routes.draw do resources :folders, only: [:new, :create, :show] end

Step 9: Start the server

Start your Rails server using,

rails server

Visit 'http://localhost:3000/folders/new' in your browser to see the upload form. After uploading a file, you should be able to view and download it on the folder's show page.

Output

Conclusion

In conclusion, file uploading in Ruby on Rails is easy to set up and use. With Rails' built-in features, you can quickly add file upload functionality to your app. This method lets users upload files through simple forms and manages those files efficiently on the server. Rails makes handling file uploads straightforward, ensuring that you can focus on building your app without worrying about complex file management issues.