How to get started with The Composable Architecture 📱
Hi 👋
What a year it has been for this newsletter!
I sent the very first email on January 31st, and now, 42 emails later, we’re already reaching the last email of the year.
I have a big thank you to all of you for your support throughout this year!
Enjoy your holiday season and I’ll see you all back in 2024 🥂
(picture from the amazing winter party at PhotoRoom)
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There’s a good chance that you’ve heard of The Composable Architecture (or TCA) at one point or another.
Even if, like me, you’ve never used it, this architecture pattern for building iOS apps has become so popular over the past years that you’re bound to have heard of it.
And maybe, also like me, you’ve been wondering what was the best way to get started if you wanted to learn how this architecture works? 🤨
As it turns out, learning TCA might be easier than you might think!
Because the creators of TCA did a great job of putting together a long tutorial that progressively introduces and explains all the key concepts.
So if you want to ramp up your TCA skills, I really recommend that you give it a look!
I actually covered the first part of this tutorial during a livestream, so here’s a quick summary of what the tutorial will teach you!
#01 – Writing Your First Feature
A Feature is the basic building block of TCA, its goal is to encapsulate state and business logic.
The idea behind a Feature is both simple and elegant:
a
Featureexposes its currentStateit also exposes a list of
Actionit can receivefinally, it implements a
Reducer, which updates the currentStatewhen anActionis received
#02 – Adding Side Effects
Of course, seeing the example above, you might be thinking that this is too simple to implement a real world iOS app.
For instance, how can a network call, or any other asynchronous operation, fit within this simple model?
That’s when Effect comes into play!
Effect is TCA’s way of implementing a side effect.
Once again, the way it works is quite elegant:
after a
Reducerhas processed anAction, it can emit anEffectand when that
Effectcompletes, it can in turn emit anotherAction……which will contain the result of the
Effectand will be processed to update theStateaccordingly ✌️
#03 – Testing Your Feature
As you can see, writing an app using TCA requires a bit of additional code in order to make everything fit within the architecture.
But this extra code has not been written in vain, because one of the great features of TCA is that the code you write is pretty easy to test!
Because our State and Action have been nicely encapsulated, writing a test becomes as simple as sending an Action and then describing the expected changes to the State:
And even side effects are fairly easy to test:
we can inject mocked version of our dependencies
and we can assert that an
Effecthas indeed sent anAction👌
As we’ve seen, TCA is a pretty interesting approach to writing iOS apps!
And even if you don’t plan to adopt this architecture, I would still recommend that you follow its tutorial: TCA makes use of a lot of very smart ideas, and knowing them can only make you a better engineer 😌
That’s all for this email, thanks for reading it!
If you’ve enjoyed it, feel free to forward it
to your friends and colleagues 🙌
I wish you an amazing week!
❤️
