Let's Build Something New

Let’s build something totally new today! It has been snowing all weekend, and my town is covered in a fluffy white blanket. Perfect conditions for the creation of a thing.


We are going to create an add-on to Pageflow. Specifically, we are about to create a connection between it and Localfocus. We want to display pretty graphs easily! Editors should be able to paste a URL in a field and magic should happen. MAGIC.

Since Pageflow has been through a big change in code, there aren’t many tutorials teaching the new, correct, way. If you follow this one, step by step, at the end you’ll have a working add-on. Okay, you can skip where I made a mistake. Let’s do this!

The code for this excercise is on GitHub.

Let's Do This!

Reading the docs

The first order of business is readin’ some documentation. With what we are trying to accomplish, the document Creating a Pageflow Plugin Rails Engine is the way to go. The bulk of which, incidentally, or maybe not so much, was written by yours truly!

1: create a rubygem

Our plugin name is going to be pageflow-localfocus. We are modelling it after pageflow-chart as they do more or less exactly the same thing. Following the instructions, we use Bundler to get started:

bundle gem pageflow-localfocus

That generated a bunch of files. Wow! Let’s commit them all. A brand new git repository was already created for us, and all the files were added to it too.

git commit

Time to create a new repository on GitHub, and connect it with our local one.

git remote add origin git@github.com:scrollytelling/pageflow-localfocus.git
git push -u origin master


Step 1 Complete

2: fill in the gemspec

The gemspec is a file that describes our gem. As it stands, we need to fix the TODOs that are in there. Also, we are removing the bit about not pushing to rubygems, and we add the ddependencies mentioned in the doc.

While we’re in here, let’s mention the license in the spec and also generate the actual MIT license in the repository. And while we’re still there we’ll also generate a Contributor Covenant. There should be no mistake that everyone is welcome to help with this project, and abuse of any kind is not tolerated.

3: create the Rails Engine itself

We create a new file that holds the Rails Engine code:

module Pageflow
  module Localfocus
    class Engine < ::Rails::Engine
      isolate_namespace Pageflow::Localfocus

In this file we are depending on something something Rails. A-ha. That means we need add Rails as a dependency in our spec.

PS: after that intial file, I added two more handy things:

  # autoload our code, which is Rails dogma
  config.autoload_paths << File.join(config.root, 'lib')

  # automagically reload our React code when it changes
  # This has been fixed in newer versions of react-rails.
  initializer "pageflow-localfocus.add_watchable_files", group: :all do |app|
    app.config.watchable_files.concat Dir["#{config.root}/app/assets/javascripts/**/*.jsx*"]

Our first bit of code is in the can! But how can we see if it does something?

Enter the console:

irb(main):002:0> Pageflow::Localfocus::VERSION
=> "0.1.0"


Let’s commit the lot and move on. Next!

4: Creating a Page Type

We move on to the next piece of documentation: Creating Page Types.

First on the menu is adding the required JavaScript files. We are just following orders here. If you want to know more, there is a commit for that!

5: Registering the Page Component

Look at us! It’s not even tea time yet and we’re already created a bunch of new things today. Time to take it to the next level and create a React Component for our page type. This is also neatly described in the documentation, with one change I am making: the page component will not be in the main components.js but neatly tucked away in the components directory.

I am just copying and pasting stuff at this point with absolutely no idea as to what it does! Like this:

(function() {
  const {
    PageBackground, PageBackgroundImage, PageShadow,
    PageContent, PageHeader, PageText
  } = pageflow.react.components;

  function Page(props) {
    return (


  const {registerPageType, connectInPage, combine} = pageflow.react;
  const {pageAttributes} = pageflow.react.selectors;

  registerPageType('localfocus', {
    component: connectInPage(
        page: pageAttributes()

It sure looks impressive.

I like the way you move

So far, we’ve added boilerplate. It’s time to get dirty. All we need is an <iframe> that points to the chart. Let’s hard-code one into our component and see if that works.

But wait! What’s that? iframes and React don’t go nicely together? Of course. Nothing ever works without pain in this ‘ecosystem’. But I am just an old Unix greybeard, don’t listen to me. Let’s make React happy and jump through some hoops to throw an iframe on the page.

6: Adding the actual iframe

It seems like a smart idea to setup a ‘ref’ to the iframe, as mentioned in the React documentation. It’s the best way to maintain a relation to the DOM object, which an iframe obviously is. When you need a ref, you cannot use a pure function to create your component. So, a class it is.

class LocalfocusIframe extends React.Component {
  render() {
    return (
        ref={iframe => this.iframe = iframe}

We have just put in a random chart URL, because we wanna see something now!

The time has come to add our newest baby to our local Pageflow install. But we need to add still more boiletplate first. Time to work on the editor integration.

7: Setting Up the Editor Integration

As described, we need a Backbone view that will be displayed inside the editor.

I managed to copy and paste the ConfigurationEditorView from the doc. But sadly, more was needed. I needed an input field and a template to render with. I found inspiration in the pageflow-vr plugin which is setup very decent.

I found that I wanted my own URL input field:

  <span class="name"></span>
  <span class="inline_help"></span>
    required pattern="https://localfocus2.appspot.com/.*"
    title="Only localfocus URLs are allowed"
<div class="validation"></div>
<div class="status_container"></div>

Pageflow does provide a built-in URL field, but this doesn’t use HTML5 form field validation. Mine does and also has the url type set. Most mobile devices will tweak the keyboard, making URL entry easier.

We also need a UrlInputView to glue the whole thing together. This one is pretty large, so I won’t paste it here. Take a look at the source.

Then after banging my head against a wall for much longer than I care to admit, I just went in and chucked all my innovations and copied existing Pageflow code. Always be shippin’. :‘(

8: Localization

Finish is in sight! We need to add translation strings for our editor UI.

Once more this is expertly described in the documentation.

9: Almost there: the Plugin class

This is pretty routine; copypasta-time once more.

module Pageflow
  module Localfocus
    class Plugin < Pageflow::Plugin
      def configure(config)

The trick here is to reference our Localfocus module when we want to use this class:

def self.plugin

Because the autoload pagic has alrady seen Pageflow and doesn’t look further. Oh, autoloading, it is so nice, so automagic, I love magic!

John Dies At The End

Or, how I started seeing things.

Having created all this awesome code we need just one thing: RESULTS!


It would be a little presumptuous to publish the gem as-is and call it a day. Instead, we will activate the plugin locally and see what’s what. Time to leave our gem code alone for a bit and go back to Scrollytelling; our Rails app.

Add the under-construction gem to Gemfile:

gem 'pageflow-localfocus', path: '/Users/joost/Gems/pageflow-localfocus'

Install it:

bundle install

And add it to the Pageflow initializer:

# ... lots of config
# ... lots of config more

Progress being made. Yes, we will need more configuration once everything is done, but for now let’s fire up the ol’ Rails server and see if we can select this page type in our editor.

💢 NO! Errors are here!

But, oh no! The server won’t even start.

NameError: undefined local variable or method config for Pageflow::Localfocus::Plugin:Class

We didn’t copy-paste enough code from the documentation. We actually need to write a method in our plugin class! Duh! That’s what you get when you’re just going through the motions.

Our method should look like this:

def configure(config)

And now everything starts! Pay attention, y’all!!

We log into the editor, create a new page, and lo and behold, we can select Localfocus as the page type! (We need to fix the category; we will do that later.)

💢 NO! Errors are here!

But… nothing happens. Or, more specifically, errors are shown in the browser console:

Uncaught TypeError: constructor is not a constructor
    at child.createConfigurationEditorView (http://scrollytelling.dev/assets/pageflow/editor/api/page_type.self-34fa332454121a83e2f96da2706f603016182821520121041780d6369b666374.js?body=1:35:12)

At this point (actually, a half hour later) I realized I needed to actually configure the plugin properly. Which means adding it to components.js and the Rails asset stylesheet. Which means doing this in the Rails app:

# app/assets/javascripts/components.js
//= require "pageflow/localfocus/components"

# app/assets/javascripts/pageflow/application.js
//= require "pageflow/localfocus"

# app/assets/javascripts/pageflow/editor.js
//= require pageflow/localfocus/editor

And that worked!

💢 NO! Errors are here!

Actually, one:

SyntaxError: unknown: Unexpected token (15:5)
  13 |       );
  14 |     }
> 15 |   }());
     |      ^
  16 |

Turns out I hadn’t indented the LocalfocusIframe class properly. I blame parentheses. They are always out to get me.

💢 NO! Errors are here! IDIOT!

On to the next error, which was that LocalfocusIframe is not defined.

Well, it turns out that can’t be a pure function either. So I rewrote it into a proper class:

class LocalfocusIframe extends React.Component {
  render() {
    return (
        ref={iframe => this.iframe = iframe}

and needed to require it in the page:

const {LocalfocusIframe} = pageflow.localfocus;

Oh, and since we have two JavaScript entry points (one for public view, the other for the editor), this line needs to be at the very top of either file:

pageflow.localfocus = pageflow.localfocus || {};

💢 NO! Errors are here!

My editor fields were all messed up.

After trying in vain to wrap my head around Backbone/Marionette, I gave up and just copied the text input views from Pageflow. pageflow.inputView was my friend. I made no sudden moves, copied every line by precious line, and then my editor worked. Progress!

💢 NO! Errors are STILL here! Amateur!

Still no luck. The LocalFocus frame seemed to load, but was empty. My console had a big warning about hitting some /null URL over there. Back to you! LOL. In fact, back to me. I took out the ?api=1 parameter on the iframe source and that fixed things right back up.

Obviously all my editor UI still shows the UNTRANSLATED STRINGS because I had to purge the local cache first. Now What?

Now, nothing! After that it kind of just worked!

A LocalFocus graph embedded in a Pageflow/Scrollytelling document