In my last post, I covered what LiveView is at a high level. In this series, we’re going to dive deeper and implement a LiveView powered Markdown editor called Frampton. This series assumes you have some familiarity with Phoenix and Elixir, including having them set up locally. Check out Elizabeth’s three-part series on getting started with Phoenix for a refresher.

This series has a companion repository published on GitHub. Get started by cloning it down and switching to the starter branch. You can see the completed application on master. Our goal today is to make a Markdown editor, which allows a user to enter Markdown text on a page and see it rendered as HTML next to it in real-time. We’ll make use of LiveView for the interaction and the Earmark package for rendering Markdown. The starter branch provides some styles and installs LiveView.

Rendering Markdown

Let’s set aside the LiveView portion and start with our data structures and the functions that operate on them. To begin, a Post will have a body, which holds the rendered HTML string, and title. A string of markdown can be turned into HTML by calling Post.render(post, markdown). I think that just about covers it!

First, let’s define our struct in lib/frampton/post.ex:

Now the failing test (in test/frampton/post_test.exs):

Our render method will just be a wrapper around Earmark.as_html!/2 that puts the result into the body of the post. Add {:earmark, "~> 1.4.3"} to your deps in mix.exs, run mix deps.get and fill out render function:

Our test should now pass, and we can render posts! [Note: we’re using the as_html! method, which prints error messages instead of passing them back to the user. A smarter version of this would handle any errors and show them to the user. I leave that as an exercise for the reader…] Time to play around with this in an IEx prompt (run iex -S mix in your terminal):

Great! That’s exactly what we’d expect. You can find the final code for this in the render_post branch.

LiveView Editor

Now for the fun part: Editing this live!

First, we’ll need a route for the editor to live at: /editor sounds good to me. LiveViews can be rendered from a controller, or directly in the router. We don’t have any initial state, so let's go straight from a router.

First, let's put up a minimal test. In test/frampton_web/live/editor_live_test.exs:

This test doesn’t do much yet, but notice that it isn’t live view specific. Our first render is just the same as any other controller test we’d write. The page’s content is there right from the beginning, without the need to parse JavaScript or make API calls back to the server. Nice.

To make that test pass, add a route to lib/frampton_web/router.ex. First, we import the LiveView code, then we render our Editor:

Now place a minimal EditorLive module, in lib/frampton_web/live/editor_live.ex:

And we have a passing test suite! The ~L sigil designates that LiveView should track changes to the content inside. We could keep all of our markup in this render/1 method, but let’s break it out into its own template for demonstration purposes.

Move the contents of render into lib/frampton_web/templates/editor/show.html.leex, and replace EditorLive.render/1 with this one liner: def render(assigns), do: FramptonWeb.EditorView.render("show.html", assigns). And finally, make an EditorView module in lib/frampton_web/views/editor_view.ex:

Our test should now be passing, and we’ve got a nicely separated out template, view and “live” server. We can keep markup in the template, helper functions in the view, and reactive code on the server. Now let’s move forward to actually render some posts!

Handling User Input

We’ve got four tasks to accomplish before we are done:

1. Take markdown input from the textarea
2. Send that input to the LiveServer
3. Turn that raw markdown into HTML
4. Return the rendered HTML to the page.

Event binding

To start with, we need to annotate our textarea with an event binding. This tells the liveview.js framework to forward DOM events to the server, using our liveview channel. Open up lib/frampton_web/templates/editor/show.html.leex and annotate our textarea:

<textarea phx-keyup="render_post"></textarea>

This names the event (render_post) and sends it on each keyup. Let’s crack open our web inspector and look at the web socket traffic. Using Chrome, open the developer tools, navigate to the network tab and click WS. In development you’ll see two socket connections: one is Phoenix LiveReload, which polls your filesystem and reloads pages appropriately. The second one is our LiveView connection. If you let it sit for a while, you’ll see that it's emitting a “heartbeat” call. If your server is running, you’ll see that it responds with an “ok” message. This lets LiveView clients know when they've lost connection to the server and respond appropriately.

Now, type some text and watch as it sends down each keystroke. However, you’ll also notice that the server responds with a “phx_error” message and wipes out our entered text. That's because our server doesn’t know how to handle the event yet and is throwing an error. Let's fix that next.

Event handling

We’ll catch the event in our EditorLive module. The LiveView behavior defines a handle_event/3 callback that we need to implement. Open up lib/frampton_web/live/editor_live.ex and key in a basic implementation that lets us catch events:

The first argument is the name we gave to our event in the template, the second is the data from that event, and finally the socket we’re currently talking through. Give it a try, typing in a few characters. Look at your running server and you should see a stream of events that look something like this:

There’s our keystrokes! Next, let’s pull out that value and use it to render HTML.

Rendering Markdown

Lets adjust our handle_event to pattern match out the value of the textarea:

def handle_event("render_post", %{"value" => raw}, socket) do

Now that we’ve got the raw markdown string, turning it into HTML is easy thanks to the work we did earlier in our Post module. Fill out the body of the function like this:

If you type into the textarea you should see output that looks something like this:

Perfect! Lastly, it’s time to send that rendered html back to the page.

Returning HTML to the page

In a LiveView template, we can identify bits of dynamic data that will change over time. When they change, LiveView will compare what has changed and send over a diff. In our case, the dynamic content is the post body.

Open up show.html.leex again and modify it like so:

Refresh the page and see:

Whoops!

The @post variable will only be available after we put it into the socket’s assigns. Let’s initialize it with a blank post. Open editor_live.ex and modify our mount/3 function:

In the future, we could retrieve this from some kind of storage, but for now, let's just create a new one each time the page refreshes. Finally, we need to update the Post struct with user input. Update our event handler like this:

Let's load up http://localhost:4000/editor and see it in action.

Nope, that's not quite right! Phoenix won’t render this as HTML because it’s unsafe user input. We can get around this (very good and useful) security feature by wrapping our content in a raw/1 call. We don’t have a database and user processes are isolated from each other by Elixir. The worst thing a malicious user could do would be crash their own session, which doesn’t bother me one bit.

Check the edit_posts branch for the final version.

Conclusion

That’s a good place to stop for today. We’ve accomplished a lot! We’ve got a dynamically rendering editor that takes user input, processes it and updates the page. And we haven’t written any JavaScript, which means we don’t have to maintain or update any JavaScript. Our server code is built on the rock-solid foundation of the BEAM virtual machine, giving us a great deal of confidence in its reliability and resilience.

In the next post, we’ll tackle making a shared editor, allowing multiple users to edit the same post. This project will highlight Elixir’s concurrency capabilities and demonstrate how LiveView builds on them to enable some incredible user experiences.

Working on website front ends I sometimes use MAMP PRO to manage local hosts and Sequel Pro to manage databases. Living primarily in my text editor, a terminal, and a browser window, moving to these click-heavy dedicated apps can feel clunky. Happily, the tasks I have most frequently turned to those apps for —starting and stopping servers, creating new hosts, and importing, exporting, deleting, and creating databases— can be done from the command line.

I still pull up MAMP PRO if I need to change a host's PHP version or work with its other more specialized settings, or Sequel Pro to quickly inspect a database, but for the most part I can stay on the keyboard and in my terminal. Here's how:

Command Line MAMP PRO

You can start and stop MAMP PRO's servers from the command line. You can even do this when the MAMP PRO desktop app isn't open.

Note: MAMP PRO's menu icon will not change color to reflect the running/stopped status when the status is changed via the command line.

• Start the MAMP PRO servers:

• Stop the MAMP PRO servers:

• Create a host (replace host_name and root_path):

MAMP PRO-friendly Command Line Sequel Pro

Note: if you don't use MAMP PRO, just replace the /Applications/MAMP/Library/bin/mysql with mysql.

In all of the following commands, replace username with your user name (locally this is likely root) and database_name with your database name. The -p (password) flag with no argument will trigger an interactive password prompt. This is more secure than including your password in the command itself (like -pYourPasswordHere). Of course, if you're using the default password root is not particular secure to begin with so you might just do -pYourPasswordHere.

Setting the -h (host) flag to localhost or 127.0.0.1 tells mysql to look at what's on localhost. With the MAMP PRO servers running, that will be the MAMP PRO databases.

• Create a local database

or

    MAMP PRO's databases are stored in /Library/Application Support/appsolute/MAMP PRO/db so to confirm that it worked you can

• Delete a local database

• Export a dump of a local database. Note that this uses mysqldump not mysql.

• Export a local dump from an external database over SSH. Note that this uses mysqldump not mysql.

• Import a local database dump into a local database

• Import a local database dump into a remote database over SSH. Use care with this one. But if you are doing it with Sequel Pro —maybe you are copying a Craft site's database from a production server to a QA server— you might as well be able to do it on the command line.

For me, using the command line instead of the MAMP PRO and Sequel Pro GUI means less switching between keyboard and mouse, less opening up GUI features that aren't typically visible on my screen, and generally better DX. Give it a try! And while MAMP Pro's CLI is limited to the essentials, command line mysql of course knows no limits. If there's something else you use Sequel Pro for, you may be able to come up with a mysql CLI equivalent you like even better.

During the winter 2020 Pointless Weekend, we built TrailBuddy (working app coming soon). Our team consisted of four developers, two project managers, two front-end developers, a digital-analyst, a UXer, and a designer. In about 48 hours, we took an idea from Jeremy Field’s head to a (mostly) working app. We broke up the project in two parts:. First, a back-end that crunches trail, weather, and soil data. That data is exposed via a GraphQL API for a web app to consume.

While developers built the API, I built a static front end using Next.js. Famously, static front-ends don’t have a database, or a concept of “users.” A bit of functionality I wanted to add was saving favorite trails. I didn’t want to be hacky about it, I needed some way to add users and a database. I knew it’d be hard for the developers to set this up as part of the API, they had their hands full with all the #soil-soil-soil-soil-soil (a slack channel dedicated solely to figuring out our soil data problem—those were plentiful.) I had been looking for an excuse to use Userbase, and this seemed like as good a time as any.

A textbook Userbase use case

“When would I use it?” The Usebase site lists these reasons:

• If you want to build a web app without writing any backend code.
• If you never want to see your users' data.
• If you're tired of dealing with databases.
• If you want to radically simplify your GDPR compliance.
• And if you want to keep things really simple.

This was a perfect fit for my problem. I didn’t want to write any more backend code for this. I didn’t want to see our user’s data, I don’t care to know anyone’s favorite trails.* A nice bonus to not having users in our backend was not having to worry about keeping their data safe. We don’t have their data at all, it’s end-to-end encrypted by Userbase. We can offer a reasonable amount of privacy for free (well for the price of using Userbase: $49 a year.) I am not tired of dealing with databases, but I’d rather not. I don’t think anyone doesn’t want to simplify their GDPR compliance. Finally, given our tight timeline I wanted nothing more than to keep things really simple.

Using Userbase

Userbase can be tried for free, so I set aside thirty minutes or so to do a quick proof of concept to make sure this would work out for us. I made an account and followed their Quickstart. Userbase is a fundamentally easy tool to use, but their quickstart is everything I’d want out of a quickstart:

• Written in the most vanilla way possible (just HTML and vanilla JS). This means I can adapt it to my needs, in this case React using Next.js
• Easy to follow, it does the most barebones tour of the functionality you can expect to get out of the SDK (software development kit.) In other words it is quick and it is a start
• It has a live demo and code samples you can download and run yourself

It didn’t take long after that to integrate Userbase into our app with more help from their great docs. I debated whether to add code samples of what we did here, and I didn’t because any reader would be better off using the great quickstart and docs Userbase provides—they are that clear, and that good. Depending on your use case you’ll need to adapt the examples to your needs, for us the trickiest things were creating a top level authentication context to manage users in the app, and a custom hook to encapsulate all the logic for setting, updating, and deleting favourite trails in the app. Userbase’s SDK worked seamlessly for us.

Is Userbase for you?

Maybe. I am definitely a fan, so much so that this blog post probably reads like an advert. Userbase saved me a ton of time in this project. It reminded me of “The All Powerful Front End Developer” talk by Chris Coyer. I don’t fully subscribe to all the ideas in that talk, but it is nice to have “serverless” tools like Userbase, and all the new JAMstacky things. There are limits to the Userbase serverless experience in terms of scale, and control. Obviously relying on a third party for something always carries some (probably small) risk—it’s worth noting Usebase includes a note on their pricing page that says “You can host it yourself always under your control, or we can run it for you for a full serverless experience”—Still, I wouldn’t hesitate this to use in future projects.

One of the great things about Viget and Pointless Weekend is the opportunity to try new things. For me that was Next.js and Userbase for Trailbuddy. It doesn’t always work out (in fact this is my first pointless weekend where a risk hasn’t blown up in my face) but it is always fun. Getting to try out Userbase and beginning to think about how we may use it in the future made the weekend worthwhile for me, and it made my job on this project much more enjoyable.

*I will write a future post about privacy conscious analytics in TrailBuddy when I’ve figured that out. I am looking into Fathom Analytics for that.