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How to Generate PDF from HTML Using Grover in Rails

Marcelo | Founder

Nov 1, 2024

Overview of Grover as a PDF Library and PDF API

Grover is a PDF library in the Ruby ecosystem, leveraging the capabilities of Puppeteer, a Node.js-based tool for automating browser actions.

Unlike other Ruby PDF libraries, Grover excels in translating HTML and CSS directly into visually precise PDF documents. It offers a unique blend of control, allowing for advanced PDF customization through Puppeteer’s API while maintaining a Rails-friendly syntax.

You can check out the documentation here.

Comparison Between Grover and Other Ruby PDF Libraries

Number of downloads from bestgems of Grover

Ruby offers a range of PDF generation libraries, each with unique features:

• WickedPDF and PDFKit: Both use wkhtmltopdf, which is reliable but lacks modern CSS support. Grover, using a headless browser, has far superior handling of complex CSS.

• HexaPDF and Prawn: Designed primarily for programmatic PDF creation rather than HTML-to-PDF conversion, offering more granular control but demanding extensive setup for custom layouts.

• Puppeteer-Ruby: While it uses Puppeteer directly, integrating it with Rails requires additional boilerplate code, where Grover simplifies these processes by streamlining the setup for Rails environments.

Grover stands out by offering a direct route from HTML templates to professional-grade PDF documents, making it ideal for developers looking to implement dynamic, aesthetically refined PDF reports on their SaaS applications.

Guide to generate pdf from html using Ruby on rails grover

Setting Up Grover in a Rails Environment

Installing Grover: Required Dependencies and Setup

To use Grover, start by adding it to your Rails project’s Gemfile:

gem 'grover'

After adding the gem, run bundle install. Grover relies on Puppeteer, which needs a Node.js environment. If Node.js is not installed, use a package manager like Homebrew:

brew install node

You’ll also need to install Puppeteer to ensure compatibility:

Project Folder Structure

For a clean project, consider setting up folders for organization:

Storing HTML templates in app/views/pdf_templates keeps your code organized and helps in separating PDF-specific HTML from other views.

Configuring Grover in Rails for HTML to PDF Conversion

In config/initializers/grover.rb, set up basic Grover configuration options:

Grover.configure do |config|
  config.options = {
    format: 'A4',
    margin: { top: '1cm', bottom: '1cm' },
    display_url: 'http://localhost:3000'
  }
end

These settings ensure your PDFs are in A4 format with standard margins, suitable for most SaaS report requirements.

Common Configuration Options and Settings for Grover

Grover provides multiple options to refine PDF output:

Viewport size: Control page dimensions.
Emulate media type: Allows PDFs to use specific CSS (e.g., screen or print).
JavaScript execution: Allows JavaScript to be run within the HTML before rendering, which is useful for dynamic data updates.

Example:

config.options[:viewport] = { width: 1024, height: 768 }
config.options[:emulate_media] = 'screen'
config.options[:wait_until] = 'networkidle0'

Integrating Grover with Rails Controllers and Views

Within the controller, use Grover to convert an HTML view into a PDF:

class ReportsController < ApplicationController
  def show
    html_content = render_to_string(template: 'pdf_templates/invoice')
    pdf = Grover.new(html_content).to_pdf
    send_data pdf, filename: "invoice.pdf", type: 'application/pdf'
  end
end

This example pulls an HTML template, converts it to PDF, and streams it as a downloadable file.

Creating HTML Templates for PDF Reports

Designing Responsive HTML Templates for PDF Output

The HTML structure plays a key role in PDF appearance. Here’s an example for an invoice template:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Invoice</title>
  <style>
    body { font-family: Arial, sans-serif; margin: 0; padding: 20px; }
    .invoice { width: 100%; max-width: 800px; margin: auto; }
    .header { font-size: 24px; font-weight: bold; text-align: center; }
    .details { display: flex; justify-content: space-between; margin-top: 20px; }
    .footer { text-align: right; font-size: 14px; }
  </style>
</head>
<body>
  <div class="invoice">
    <div class="header">Invoice</div>
    <div class="details">
      <div>Customer Name: <%= @customer.name %></div>
      <div>Date: <%= Date.today %></div>
    </div>
    <table>
      <!-- Add table rows for items and prices -->
    </table>
    <div class="footer">Thank you for your business!</div>
  </div>
</body>
</html>

Adding Dynamic Data to PDF Reports from Rails Models

Fetch data from Rails models to enrich the PDF report:

<% @invoice.items.each do |item| %>
  <tr>
    <td><%= item.name %></td>
    <td><%= item.price %></td>
  </tr>
<% end %>

This example loops over invoice items, inserting each into the PDF as a table row.

Error Handling and Debugging Common Issues in PDF Generation

Troubleshooting Grover issues can involve:

Checking network connectivity: Ensure images and external resources are accessible.
JavaScript execution issues: Certain JavaScript code may not render; test separately and simplify as needed.
CSS quirks: Some CSS properties behave differently in PDF; adjust with print-specific CSS if necessary.

Example debugging solution:

begin
  pdf = Grover.new(html_content).to_pdf
rescue StandardError => e
  Rails.logger.error("PDF generation error: #{e.message}")
end

Advanced PDF Customization Options with Grover

Grover supports numerous customization options, like header and footer elements, for branding:

config.options[:display_header_footer] = true
config.options[:header_template] = "<div class='header'>Company Invoice</div>"
config.options[:footer_template] = "<div class='footer'>Page <span class='pageNumber'></span></div>"

How to Use a PDF API to Automate PDF Creation at Scale

For SaaS platforms, automating PDF generation at scale might require offloading the heavy lifting to a PDF API.

It's also an option to integrate with third-party APIs like pdforge you can handle high-volume PDF generation, complex formatting, and post-processing, all from a single backend call.

Here’s an example of how to integrate pdforge in Rails to convert HTML content into a PDF via an API call:

require 'net/http'
require 'json'
require 'uri'

class PdfApiService
  def self.generate_pdf(html_content)
    uri = URI("https://api.pdforge.com/v1/pdf/sync")
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    request = Net::HTTP::Post.new(uri.path, {
      'Content-Type' => 'application/json',
      'Authorization' => "Bearer your-api-key"
    })
    request.body = {
      templateId: 'your-template',
      data: { html: html_content }
    }.to_json
    response = http.request(request)
    response.body if response.is_a?(Net::HTTPSuccess)
  end
end

This code sends a POST request to the pdforge API, receives the generated PDF, and saves it locally.

Conclusion

Grover is an ideal choice for Ruby on Rails applications needing flexible, high-quality PDF generation directly from HTML. With Grover, it’s possible to maintain brand-consistent, dynamic reports without sacrificing the visual precision that CSS provides.

Other libraries like WickedPDF or HexaPDF may suit simpler tasks, while Prawn is better for highly structured, custom layouts.

Meanwhile, for scalable, automated PDF generation, third-party APIs like pdforge are the optimal choice for high-demand applications.