forsbergplustwo

Generating PDFs in Ruby, using Ferrum gem on Heroku

by Bjorn Forsberg

Ferrum is a pure Ruby gem, providing a high-level API to control Chrome, which runs headless by default. Ferrum is a great alternative to Node's Puppeteer library, which is a pain to use with Ruby and Heroku.

Ferrum can be used for any browser scripting work, as well as for generating screenshots and PDFs. We use it mainly for PDF generation, hosted on Heroku, and the setup flow goes like this:

1. Add Chromium locally if not already done: brew install chromium

forsbergplustwo

# my_engine/my_engine.gemspec

spec.add_dependency "importmap-rails", "~> 0.7.6"

forsbergplustwo

#   # USAGE
#
#   # Include the concern in the class
#   class Settings::CreateSetting
#     include SimpleServiceObject
#
#     # optional: include validation
#     validates :shop, presence: true
#
#     # mandatory: initialize the command with keyword arguments

forsbergplustwo

require 'json'

class GraphqlResponseRubyfier
  def initialize(response)
    @response = JSON.parse(response)
  end

  def rubyfy
    rubyfied_response = to_o(@response)
    puts(rubyfied_response)

forsbergplustwo

require "ruby-boolean"
class TypeValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    value_to_test = type_before_coercion(record, attribute, value)
    expected_type = type_class(options[:with])

    record.errors.add attribute, (options[:message] || "argument of #{record.class} is not of class: #{options[:with].to_s.camelize}. It is class: #{value.class} with value of #{value}") unless value_to_test.is_a?(expected_type)
  end

  private

forsbergplustwo

Installing a Gem on Heroku from a Private GitHub Repo

Sometimes you want to use a gem on Heroku that is in a private repository on GitHub.

Using git over http you can authenticate to GitHub using basic authentication. However, we don't want to embed usernames and passwords in Gemfiles. Instead, we can use authentication tokens.

This method does not add your OAuth token to Gemfile.lock. It uses bundle config to store your credentials, and allows you to configure Heroku to use environment variables when deploying.

1. Generate an OAuth token from GitHub

forsbergplustwo

  CollectionsQuery = <<~GRAPHQL
    {
      shop {
        name
      }
      collections(first: 15, sortKey: UPDATED_AT, reverse: true) {
        edges {
          node {
            id
            title

forsbergplustwo

!function() {
    var e = function(e) {
        var t = {
            exports: {}
        };
        return e.call(t.exports, t, t.exports),
        t.exports
    };
    e(function() {
        "use strict";

forsbergplustwo

Return-Path: <info@forsbergplustwo.com>
Delivered-To: bjorn@forsbergplustwo.com
Received: from director1.mail.unoeuro.com ([172.17.165.33])
	by worker6.mail.unoeuro.com (Dovecot) with LMTP id +ZWcANlN5lhr2wAAao8G7A
	for <bjorn@forsbergplustwo.com>; Thu, 06 Apr 2017 16:16:57 +0200
Received: from worker3.mail.unoeuro.com ([172.17.165.33])
	by director1.mail.unoeuro.com (Dovecot) with LMTP id 6YBwF9lN5lgFOAAA1VGibg
	; Thu, 06 Apr 2017 16:16:57 +0200
Received: from localhost (localhost [127.0.0.1])
	by worker3.mail.unoeuro.com (Postfix) with ESMTP id 57C01160074

forsbergplustwo

Return-Path: <info@forsbergplustwo.com>
Delivered-To: bjorn@forsbergplustwo.com
Received: from director1.mail.unoeuro.com ([172.17.165.10])
	by worker6.mail.unoeuro.com (Dovecot) with LMTP id y97tLkpO5lg93gAAao8G7A
	for <bjorn@forsbergplustwo.com>; Thu, 06 Apr 2017 16:18:50 +0200
Received: from worker14.mail.unoeuro.com ([172.17.165.10])
	by director1.mail.unoeuro.com (Dovecot) with LMTP id G5uTLEpO5lgPOAAA1VGibg
	; Thu, 06 Apr 2017 16:18:50 +0200
Received: from localhost (localhost [127.0.0.1])
	by worker14.mail.unoeuro.com (Postfix) with ESMTP id AB088E0070