How I Fixed: React Native – Warning: Functions are not valid as a React child. This may happen if you return a Component instead of from render. Or maybe you meant to call this function rather than return it.

This one had me kicking myself.

What you see on your phone

I really like VSCode for JS projects, but man-oh-mally, on this occasion it bit me. I wonder if I need another plugin, or something?

Bit easier to see in Chrome developer tools debugging session

The error in full for Google searchers:

Solving this, for me, was actually really straightforward. The issue was a typo of fail proportions.

I’d been playing around with using functional components with React Native, instead of the more typical (from all the examples I’ve seen anyway) class component approach:

Pretty basic, right? I always feel somehow much worse about myself when my most basic creations fail unexpectedly.

The problem is (as best I can tell) a syntax error. But neither VSCode nor WebStorm flag this up.

Ok, so to put us all out of our misery:

But why doesn’t the IDE flag this?

I’m not sure how this initial fat arrow could ever be valid syntax? I’ve tried playing around in the console and I can’t seem to make it work.

Anyway, hopefully for you, it’s something similar if not identical. Fat fingers, fat arrows.

[ReactJS] I Still Find Too Many People Who Don’t Know This Cool Tip

If you have:

You don’t need the

You can just use:

And get the same outcome.

It reads a lot nicer.

The 2018 Beginners Guide to Back End (JSON API) + Front End Development

It’s been a few weeks in the making, but I am happy now to reveal my latest course here on CodeReviewVideos:

The 2018 Beginners Guide to Back End (JSON API) + Front End Development.

This course will cover building a JSON-based API with the following back-end stacks:

  1. ‘raw’ Symfony 4 (PHP)
  2. Symfony 4 with FOSRESTBundle (PHP)
  3. API Platform (PHP)
  4. Koa JS (JavaScript / node)

Behat will be used to test all of these APIs. One Behat project, four different API implementations – in two different languages (PHP and JS).

We’re going to be covering the happy paths of GET , POST , PUT , (optionally) PATCH , and DELETE.

We’ll also be covering the unhappy paths. Error handling and display is just as important.

Where possible we’re going to try and use just one Behat feature file. It’s not always possible – the various implementations don’t always want to behave identically.

There’s a ton of good stuff covered in these videos. But the back end is only half the battle.

Whether you want to “catch them all”, or you’re working with a dedicated front-end dev, it’s definitely useful to know the basics of both.

With that in mind, you can pick and choose whether to implement the back-end, or front-end, or both.

If you don’t want to implement a back-end yourself, cloning any of the projects and getting an environment up and running is made as easy as possible by way of Docker. But you don’t need to use Docker. You can bring-your-own database, and do it that way, too.

The Front End

Whatever back end you decide to spin up, the front end should play nicely.

We’re going to implement a few different front-ends. The two I’m revealing today are:

  1. ‘raw’ JavaScript
  2. React

I have plans for a few others, but each implementation is a fair amount of work and I don’t want to over promise at this stage. There’s definitely at least two more coming, but let me first get these two on the site 🙂

The raw JavaScript approach aims to show how things were in the ‘bad old days‘. The days before your package manager  would take up ~7gb of your hard disk with its cache  directory.

The benefit of working this way is that there’s really no extra ‘stuff’ to get in the way. We can focus on making requests, and working with responses.

But that said, this is 2018 and the many modern JavaScript libraries and frameworks are fairly awesome. You’ll definitely get a renewed sense of appreciation for how much easier your life is once you’re comfortable using a library like React, after having done things the hard way.

Again, as mentioned we will cover more than just raw JS and React. Currently each implementation is between ten and fifteen videos. Each video takes a couple of hours to write up, and another couple of hours to record on average. I’m going as fast as I can, and will upload and publish as quickly as possible.

You can watch them as they drop right here.

Site Update

Behind the scenes over the past 10 weeks I have been working on integrating CodeReviewVideos with Braintree.

This is to enable support for PayPal.

I tried to create a ticket for everything I could think of ahead of starting development.

And I added a new ticket for any issue I hit during development. I’m not convinced I tracked absolutely everything, but even so I completely underestimated just how much work would be involved in this feature.

Being completely honest, I have never been more envious of Laravel’s Spark offering. For $99 they get Stripe and Braintree integration, and a whole bunch more. Staggering.

There’s a bunch of other new and interesting features in this release.

I’ve taken the opportunity to migrate from Symfony 3 to Symfony 4 for the API. There’s a bunch of new issues that arose during this transition – I hadn’t given it much prior thought, but with the new front controller ( public/index.php) totally broke my Behat ( app_acceptance.php) setup.

This work is also enabling the next major feature which I will start work on, once PayPal is live. More on that in my next update.

I appreciate that from the outside looking in, there doesn’t seem to have been a great deal of activity on the site over the last few weeks. I can assure you that behind the scenes, there has never been more activity.

Have A Great Weekend

Ok, that’s about it from me for the moment.

As ever, have a great weekend, and happy coding.

p. s. – I would be extremely grateful if you could help me spread the word by clicking here to tweet about the new course.

Why I Love React 16

Fragments are the feature I intuitively expected in React 15.

They are a really welcome addition to React 16.

This is now valid:

Notice that the horizontal rule, and a full component are being returned inside an array.

The official announce post has another example.

I love React. Thank you to everyone involved in getting this new release out of the door, and thank you to everyone in the React community for making my time with the front end a heck of a lot more enjoyable than it used to be.

PHP > React > Server Side Rendering > PHP

Back when I was a server room techy there was a line my old boss used to say whenever I got wind of something new and shiny:

There are no new ideas in IT, just the same ones on repeat.

Of course he was being tongue-in-cheek, but there was a truth in what he said.

For example, around the time I was in this role, the IT industry was moving from distributed to centralised. That is to say we had a bunch of servers dotted all over the county, and the plan was to bring them into just two central server rooms.

This, I was assured, was very much like “the olden days” when individual desktops were replaced with “dumb terminals”, which relied heavily on a centralised Mainframe.

At some point, someone (likely an army of well paid consultants) espoused the failings of such an architecture (oh my, single point of failure!) and likely sold them a bunch of high powered standalone desktops.

This worked well for a while, then companies like Citrix came along and sold a different spin on “dumb terminals” using your existing high powered desktop, and so on, and so on.

What the heck does any of this have to do with Web Development, I hear you ask.

Good question.

As you may recall, I have been getting quite excited about launching the new, shiny revision of I had my zip lock baggy of party poppers at the ready. Things were looking super.

Then, over the previous weekend, it dawned on me:

How’s the SEO on this new site then?

Seeing as about 70% of the incoming visitors to CodeReviewVideos arrive via Google, I figured I should probably – ya’ know – give this some consideration.

I checked, and it turned out that I had, ahem, neglected to set any of the head information.

Yes, I felt quite the chimp.

But not to worry, I have all the SEO data just sat ready and waiting in the DB. After all, it’s exactly the same as for the existing site.

What happens with the existing site is what happens with pretty much any PHP site I have ever worked with:

  • A request comes in
  • The relevant data is fetched from the DB (thanks, Doctrine)
  • This data populates a template (thanks, Twig)
  • The response is returned to the end user (thanks, Symfony!)

It doesn’t matter if the request is from Google Bot, or from a real person. The process is always the same.

What this means is that the response contains everything needed to make a full page representation.

Google Bot can look at the page and see all the expected “stuff”: the header tags, and body content, it’s all there.

Sure, we can then augment this with a snazzy bit of JS here and there, but largely, it’s good to go.

Web 2 Point… Oh?!

Then sometime a few years back, Single Page Applications (SPA, and not the relaxing kind) became popular.

SPA – not as relaxing as you may have been led to believe

Fast forward a few years and boom, I’ve done a few of these here SPA’s with React and Angular, and I’m thinking: yeah, this is awesome, let’s make CodeReviewVideos all snazzy using all this wicked tech.

So I did.

The new version of the site uses React, and Redux, and Redux Saga, and it talks to a Symfony JSON API, and it’s all lovingly tested and fills me with warm fuzzy feels whenever I work with either code base.

Unfortunately, all this awesomeness does make the architecture more complex. Let’s revisit how a request / response works now:

  • A request comes in
  • The user gets sent this:

  • We are done, let’s go to the pub.

If you’re a bot Yahoo, Bing, or Yandex, you’re now done.


By all accounts these bots do not process JavaScript, so forgettaboutit.

This may very well be of no major consequence.

By way of some hard figures, the combined total visitors that CodeReviewVideos received over the last 7 days that came via a search engine that isn’t Google was:


Fixing the world for the sake of these other search engines probably isn’t worth my time right now.

But Google… well, we must do better.

Now, it turns out that maybe Google has already solved this problem.

My guess is they have. I mean, this is Google. They are super smart, and it’s their job to get this right.

But can I risk killing the site on a maybe.

No, definitely not.

What Happens Next?

Back to the HTML from above. Thinking about the request / response sequence, what happens next?

Well, on the client side – which is to say in your visitor’s browser – assuming they have JavaScript enabled, the JS is read and run (or parsed and executed, if you’re a CS text book).

Cus i’m Shiny!

This is where all the cool stuff happens!

  • React builds the page from my components
  • The components instruct the browser to make requests to the back-end API for the real content
  • The real content is received
  • React renders the content into the right place(s)
  • The visitor is completely indifferent

By the way, if the visitor doesn’t have JavaScript enabled then they are going to have a bad time. But, ya know, 2017, etc, etc.

When I realised my mistake about SEO last weekend, my first thought was to simply grab my Helmet and populate the head tags using the API response.

Alas, as we have now seen, this simply will not do.

So I figured I would be a Smart Guy ™ and put a caching layer in front of my web server. Maybe I could trick the bots by returning a fully cached version of each page.

Yeah, that didn’t work.

At this point I had a short breakdown.

Fortunately, PHP North West happened which took my mind off of the problem.

Ultimately though, it meant I had to postpone the scheduled launch. And that sucks.

Server Side Rendering anybody? No? SSR? No?

Of course I’m not the first person to have experienced this problem.

There is already a solution:

Server Side Rendering.

The idea here is rather convoluted, but stick with me:

We already have our shiny new React site, right? Yes, yes we do.


So, let’s get a Node JS instance to sit in front of our React site, and uses some of the stuff we learned in the Dark Arts class at Hogwarts to run this code, then convert the response to a string, and write the string to a template, which is turned into another string which is sent back to the browser so that we now have the necessary HTML to please Google like in the olden days.

Oh my.

It seems like we’re repeating ourselves here.

But now with more layers. More bug filled, confusing, maybe unnecessary layers.

Anyway, that’s where I’m at with CodeReviewVideos right now. Trying to migrate my existing front end code from client-side only, to this SSR setup to essentially reproduce the outcome I already have with plain old PHP.

What this means is right now I have no ETA on the next version, and once it is again “ready”, I will need to go back through a phase of testing before go-live.

Video Update

This week saw three new videos added to the site:

#1 – [Part 1] – Twig Extensions – How to add a custom CSS class to an invalid form field

Between this, and the next video we look at a question I got asked late last week:

How can I add a custom CSS class to the input / other form field when validation fails for that field?

This video explores one possible solution to this problem.

What happens however, is that we end up with a bunch of repeated logic living in a Twig template.

Generally, if you find yourself repeating yourself… or you end up with complex logic living inside a Twig template, you can probably extract it into a better location – a custom Twig function.

#2 – [Part 2] – Twig Extensions – Create a Twig Extension Function to Keep DRY

As such we look at extracting this repeated logic from our Twig template into a Twig Extension.

It’s one of those topics that sounds like it might be hard, or too nerdy, or whatever.

It’s just a strange name for a very useful concept.

If you use Twig in any seriousness, and you don’t yet know about Twig Extensions then this video should help you understand how to use one, and why it’s not as hard as you might think to do so.

#3 – Docker Elixir Phoenix – Part 1 – The Web Server

In my personal experience there has been no better way to improve my overall knowledge of software development than by learning another language.

Elixir, in this case, is the language.

Phoenix is somewhat akin to Symfony, or Rails, or what have you. It’s a framework for web applications.

In this series we are building up a small but functional (ho, ho) JSON API using Elixir and Phoenix.

In this video we cover how to set up the Web server by way of docker-compose.yml. This series is a little more advanced than most of the content on CodeReviewVideos, but I hope you’re finding it enjoyable all the same.

That’s It, That’s All

That’s just about it from me this week.

My favourite snowboarding movie 🙂 Great soundtrack.

As mentioned last week I spent the previous weekend at the PHP North West conference.

You can read about my time there right here.

There are pictures 🙂 and also a lesser spotted Rasmus found in his natural habitat.

Have a great weekend, and happy coding.