Touchlab & Square Collaborating on Kotlin Multiplatform

Touchlab & Square Collaborating on Kotlin Multiplatform

My professional career started in college with Java 1.0. I started working during the bright Write-Once-Run-Anywhere heyday. We were finally going to get one platform!

Well, we know how that went. Java failed as a consumer UI platform. However, as a vehicle of portable logic, Java has been one of the biggest success stories in computers.

Thus one of my favorite quotes:

Shared UI is a history of pain and failure. Shared logic is the history of computers.

-Kevin Galligan (me)

I have been fixated on this for the last few years, because the need is obvious, as seems the opportunity. Native mobile, Android and iOS, are almost identical under the UI. They are architecturally homogenous. The web, although somewhat different, still needs mobile-friendly logic, and as WebAssembly matures, will look increasingly like native mobile at an architectural level.

Kotlin Multiplatform is a great entry into the pool of options for shared logic. It natively interops with the host platform, allowing optional code sharing. The tools are being built by JetBrains, so as the ecosystem matures, we can expect a great developer experience. Kotlin is also very popular with developers, so over the long term, Kotlin Multiplatform adoption is pretty much assured.

I believe in its future enough to move my role at Touchlab to be almost entirely Kotlin Multiplatform R&D. That means I code and speak about open source and Kotlin Multiplatform. As a business, we’ve pivoted Touchlab to be the Kotlin MP shop. We are of course still native mobile product experts, but we are also looking forward to helping clients leverage a shared, mobile-oriented architecture as the future of product development.

Square’s Jesse Wilson recently announced his team’s commitment to Kotlin Multiplatform.

We are super excited to get to work with them on improving the developer experience and catalyzing the KMP ecosystem. It would not be an exaggeration to say that this team, and Square more broadly, is responsible for much of what the Android community considers best practice, if not the actual libraries themselves.

To be successful for native mobile, Kotlin Native needs to be something that Swift developers feel is productive and at least somewhat native to their modern language and environment. I think also selling iOS developers on Kotlin as a language and platform is important. This will largely be our focus for the near future.

Will it work out? We’ll see. In as much as it’s possible to make Kotlin native to iOS, I think we have one of the best possible teams to help us find out. I am very much looking forward to the challenge.

Learning More about Kotlin Multiplatform 

If you want to learn more about Kotlin Multiplatform here are a couple resources:

The Case for Kotlin: Risk-Free, Cross-Platform, Future-Friendly… and Ready to Work – Right Now

The Case for Kotlin: Risk-Free, Cross-Platform, Future-Friendly… and Ready to Work – Right Now

It’s madness, really.

An app is written for the Web.

Then, it’s written for Android.

Same app, different code.

Oh, and it needs be written for iOS, too. At the same time.

Again, different code. The question is, “Why?”

Development teams are essentially tripling their coding and testing efforts to ensure cross-platform coverage. It’s costly. It’s time-consuming. And – this might be the craziest part – it’s uncertain what the shelf life of the code will be. As we know, the future is unwritten.

As always, the goal is to be able to implement products more efficiently, and with better testing across platforms. And up to now, every cross-platform coding solution that has come along really hasn’t worked that well.

The good news is that there is now a better way. And a proven way.

We at Touchlab have been writing code in Kotlin and deploying it to Android and iOS platforms, with no hiccups.

That’s why we’ve gone all-in with Kotlin.

Kotlin is a true multiplatform language

Kotlin enables you to write once, and test once. No siloed development teams. The same code can be used across Android, iOS and Web apps with no changes, eliminating the need for a translation layer. In essence, you’re reducing the amount of business logic coded by frontend developers by consolidating it efficiently with native code, but not oversimplifying abstractions.

What’s not to love about that?

No wonder there’s a groundswell of enthusiastic support in developer communities around the world. There are 1.5 million developers currently using Kotlin, with 96,000 GitHub repositories containing 100 million lines of code. And the numbers keep growing. It’s one of the top two languages that developers are hungry to learn.

Kotlin was developed as a completely new language eight years ago, built from the ground up as a pragmatic approach to coding – a way to develop cleanly, clearly, and quickly. Simply put, Kotlin is more readable, reusable, interoperable, and safer, offering a first-rate developer experience.

Kotlin is your best bet on your complete tech stack

More important, it’s a low-risk way to code because it dovetails seamlessly with the native platforms on Java, iOS, and the web. It’s a modern language that enables you to build on what you’ve already coded, without re-working or re-inventing what you already have. Plus, because the code you share is optional, you can start small and increment as desired.

Kotlin is really an extension of Java, so it’s not a big leap for Java developers to start using Kotlin at all.  In other words, you don’t have to make a big, potentially expensive decision to get started.

In fact, on Android, Kotlin was built for direct JVM interoperability. On iOS, Kotlin is ready for prime time, and the first half of 2019 will see rapid mainstream adoption. And Google officially recommends Kotlin as a language of choice.

The big considerations for any development team are cost, time, resources, and risk. And the big problem with the siloed approach is that organizations are often tripling them.

At the same time, the wrong teams are working on the wrong projects. Back-end developers should focus on architecture as well as APIs – but not UI. Enabling your back-end developers to code and test the client and server features as a unified whole enables more rapid development with safer, higher quality and identical implementation.

Our experience with Kotlin so far?

No siloed teams. More streamlined workflows. Real cross-platform functionality.

Yes, it’s working now!

Future of Shared Code = Kotlin Multiplatform

Future of Shared Code = Kotlin Multiplatform

If you’ve been following our development of Doppl for the last couple years, we’ve built a Gradle toolset for J2objc, an architectural structure with an Android compatible API, and published a number of popular libraries for that ecosystem. In other words, a full toolset extension of J2objc which allows sharing logic and architecture from Android to iOS.

J2objc is a mature, stable technology. If you have an iPhone, you’re more likely to have some J2objc in there than all the other non-HTML frameworks put together. J2objc makes sense not because it lets Java developers publish iOS code. It makes sense because it allows a platform native language produce platform native libraries, with optional code sharing, without any significant barrier or translation layer.

We use this framework with current clients, and would absolutely take new projects with it if we have the bandwidth to do so.

However, we’re officially out of the Doppl business.

The future of shared code and architecture, as far as we’re concerned, is Kotlin Multiplatform.

Some of the reasons we like it are the same as why we like J2objc. Native language, optional sharing, platform compatibility. As of the last few months, all R&D and open source development has been focused on KMP. As of KotlinConf this year (or shortly after) the tooling and libraries will be ready for production work. It is time to burn the ships.

To be better open source citizens, and to avoid internal distractions, we’ll be unpublishing Doppl and related libraries. If you’re one of the handful of orgs who use the library, please reach out and we’ll make sure you can access the repos.

I want to be clear that this doesn’t mean I think J2objc is bad tech. I still think it’s amazing technology. If you wanted to maximize your shared mobile architecture today, it would be significantly more productive than other options.

However, the community excitement around Kotlin Multiplatform is intense.

Over the next several months there will be a number of library announcements. It’s also not just for Android/iOS logic, but back end and front end architecture, including native mobile, web with JS, and webassembly. There is a lot of work to be done, but there’s a much wider scope of problems to solve.

We are, of course, looking for products and orgs interested in getting started. Also, I’m starting the search for our first Multiplatform specific engineer (besides me). Reach out.

Mobile Platform Convergence

Mobile Platform Convergence

Our last post about Mobile Oriented Architecture talked about Android, iOS, and the web beginning to look similar at an architectural level. That is a future which is a little far out, and if I’m being honest, for the web end, certainly speculative. Several things will have to come together, and regardless of how well they do, mobile and web are going to have some differences. Knowledgeable practitioners will be able to deal with these differences, but mobile and web will always be more like cousins than siblings.

However, if we think a lot closer to current reality, it’s not all bad news. The MOA diagram I posted looked like this.

Everything’s the same!

Most projects don’t really look like that, though. What the web is doing and what mobile is doing tend to differ somewhat (or significantly). What iOS and Android are doing, however, tend to be the same. The diagram should really look like this.

Mobile is usually pretty different.

Why your product’s feature set should be the same on Android and iOS should be obvious. They’re essentially the same thing. A mobile device. Unfortunately how apps are built for each is quite different. Different languages, libraries, ecosystems, etc.

The funny story here, though, is how not different they actually are. Again, architecturally speaking. They’re both unix-y systems, with files, threads, networking. Both ship with sqlite (and you can link to it). The raw components you need to actually construct the logic of your apps exists in both places, and is basically the same.


That is the general idea behind Doppl. Take some AOSP code, the architectural bits that you’re likely to use in an app, and implement them on iOS using J2objc. You construct your UI the same way you had previously, but both Android and iOS can call into a shared, tested architecture.

There’s a lot to unpack behind it. The longer blog post discussing concepts can be found here, as well as a much updated video from Droidcon SF.

That work is ongoing. We recently pulled the gradle plugin out of the Doppl project because it builds against stock J2objc now (if you tried the original j2objc gradle plugin, they’re similar but different).

Awesome! Nailed it, right?!

It is an interesting time to be pushing a Java thing in the Android community. After Google announced Kotlin support, pretty much nobody wanted to hear about Java. I very much understand this position, but the reality is, although not as sexy, J2objc is quite stable and being used by some very interesting products in production.

On the other hand, some folks are also sorta/kinda using it, but in a much more limited capacity, for a number of reasons. If you’re talking about product development in large teams, Ray’s talk is very interesting. Some shops are simply not going to try to do this kind of stuff. They have the resources to build everything separate, and have the testing and architectural discipline to do so effectively.

There’s also going to be a political issue with existing teams. Using J2objc/Doppl, your development efforts start to look like this.

It’s an Android world

The iOS team is not going to be happy about this situation. There’s no real way to spin it otherwise. Dev becomes Android focused.

This is not bad if you aren’t dealing with an established internal iOS team. In fact, it becomes a lot easier to outsource the 2nd platform, assuming you want to build Android-first. That’s another blog post in the making, but replicating something that exists is a lot easier than making a new thing.

Kotlin Multiplatform

The other tech we’re really excited about is Kotlin Multiplatform. Rather than having all the tech Android focused, there’s a real opportunity for the Android and iOS communities to come together and have a shared ecosystem. As Ray says (see the sorta/kinda video again), when using code sharing, somebody is inevitably working in a foreign environment. Kotlin is obviously Android friendly, but it is also very similar to Swift. The libraries that will need to be built are going to need solid iOS and llvm understanding. There is a real opportunity for collaboration.

There’s still a lot of work ahead of us, though. I am sure there are going to be a number of groups adding different libraries. Sometime in the near future I think we’re going to co-opt the Doppl AOSP sqlite code and see if we can make a Kotlin/Native sqlite access layer that is still source compatible with Android’s sqlite stack (support library sqlite stack, anyway).

If everything goes right, though, the diagram can look like this.

Mobile teams working together!

Technically it could look like this, but meh.

iOS first, still using Kotlin for logic and architecture

But why not ___?!

I’ll get around to the various “Why not ___?” posts at some point. The short version is, it’s not that I think those things are bad. There will be people that use them, and they will be successful. We just think that for the type of work we do, and the types of orgs we work with, these types of tech are your best bet. All of our reasoning will come down the development efficiency and risk. Again, Droidcon SF video explains it best.

Mobile Oriented Architecture (MOA)

Mobile Oriented Architecture (MOA)

Hi! I’ve had a bit of radio silence for the past few months, but there’s been quite a bit going on. New website, etc. Expect to see a few progress updates in the near future. Thought we’d start with what’s fresh on the mind.

I gave an impromptu overview of this concept yesterday to the Touchlab team. It was a bit of a whiteboard disaster, and probably a little late in the day for sweeping industry concepts. Later, at the Kotlin Meetup, I talked to two different people who kind of immediately got what I was talking about. Context is important I guess.

One of the issues while explaining to the team was, “if this happens … whenever they get around to that”. There are timelines, agendas, and moving parts involved. We have to think forward a bit.

Time Traveling

I’m just going to suspend reality here, pretend it’s the early 2020’s, and everything I want the Kotlin team, the mobile community, and the broader industry to do has happened.


It’s the 2020’s!

Mobile First

For the most part, “cross-platform” means taking web ideas and putting them onto mobile. That’s the wrong direction. Sharing code and architecture allows what we’re calling the Mobile Oriented Architecture.

MOA. Yes. Another acronym. You’re welcome.

Just a heads up. We’re talking architecture. Not UI. Not yet, anyway. UI and the features that make native native (notifications, force touch, “the notch”) are important but not part of this discussion¹.

At its most basic, MOA means applying the same code base, using mobile-tested architectural techniques, to deliver whatever client you’d like. Doing this for Android and iOS is trivial. For the web, WebAssembly (and to some degree JS) makes this feasible.

Android and iOS is trivial?

Trivial is a strong word, but the process is straightforward at least. Under the hood, they are basically the same. This was the conclusion of our J2objc/Doppl odyssey (It was also the premise, but I digress).

They are very similar systems: both are unix-y, have threads, sqlite, files, networking, etc. The Android community prefers MV* as an architectural construct. iOS apparently likes VIPER. The point of both is to make code more reliable, testable, and maintainable. The choice of either is community preference and has nothing to do with platform.

Android and iOS can be thought of as simply the “mobile platform” as far as architecture is concerned. That was true way, way back in 2018, assuming you were OK with Java (it’s the 2020’s, remember).

There are, of course, several stacks with which you could implement MOA, but the Kotlin platform is distinct for a number of reasons:

  • It is a modern language with excellent tooling.
  • On the Android side, it’s fully embraced and “native”, adding zero platform risk or impacting development efficiency.
  • The interface between “native” and “shared” is not an exception but a normal and expected part of development (aka. Smooth interoperability). For example, you don’t need to wait for somebody to wrap a library around some new iOS things. You have Swift readily available.
  • We’ve managed to convince the iOS community that embracing Kotlin/Native and multiplatform for architecture sharing is a great way to be “mobile first”, as opposed to React Native or whatever. (Again, to highlight, this is the future. Selling iOS folks is on the todo list)
  • That same iOS community has done a lot of work creating the truly multiplatform libraries needed to have efficient development.

The iOS community is, I think, one of the critical pieces that made Kotlin MOA feasible. Swift and Kotlin are very similar. Kotlin is obviously “Android leaning”, but not so much as is Java. Because Kotlin/Native doesn’t have the JVM, for better or worse, it forces a more balanced bridge between the two environments. Summary: it’s not just the “Android language”².

Back End?

Besides just sharing code, there are some interesting consequences of MOA.
When all of your code is in different languages and implemented separately, you tend to have “back end” engineers, and teams focused around the different client platforms. If you‘re implementing lots of client logic with a single code base, the “back end” engineers are going to get involved in the client code that consumes the service they’re building.

Rather than looking at the remote client as this “other” thing, it’s just a remote part of a connected system. For example, imagine a microservice style system with multiple clients. It might look something like this.

But it can look like this.

That’s not just the api call implementations. You could generate them from Swagger or similar. It’s logic, storage, offline, whatever, and all of the associated testing. Doing this in an environment without significant trade-offs with regards to development efficiency, runtime bloat, or risk is the goal.

Sounds like SOA

Sure. The mobile part is how you architect the client side and where web fits in. You’re always offline until your call succeeds. 5G is “better”, but didn’t fix the fact that you’re mobile any more than 4G fixed it. Taking what we as a community have learned from mobile and architecture, putting that together with the teams building the server side to produce mobile-focused api’s, and producing a better functioning unit is what MOA is about. The web inherits the mobile architecture⁴.


Back in 2018

But it’s still 2018

A number of things need to happen between now and then for the Kotlin version of all this to be real.

Kotlin/Native needs to be a fully baked part of the Kotlin multiplatform ecosystem. Around KotlinConf last year we were thinking this would be early 2018, but it’s not quite there yet.

If you follow progress on github, there’s some really cool stuff happening. Read the concurrency doc, for example. If you’re enough of a language nerd to know why Rust’s concurrency is cool, you’ll notice the same concepts. On the downside, reading the doc gives off the vibe that there’s going to be a lot of stuff that only functions in Kotlin/Native. If your thread sync needs to be handled in platform-specific code (and it obviously would be for JS), it’s not the end of the world, but still. Hopefully Kotlin JVM and Native aren’t too dissimilar.

We’ll need Kotlin/Native iOS-friendly libraries. I think there’s a strong pitch to make to the iOS community about why this is something they should get into, but that’ll be a whole different blog post.


We’ll have to see about WebAssembly’s progress as a standard. That’s a much bigger “if/when”. Kotlin/Native already has surprisingly good support (sample) for the current Wasm implementation, but Wasm needs a lot of the things on their post-MVP roadmap to materialize in order to be useful as a general purpose web app architecture. Threads, gc, and solid DOM access for starters. This is the part where the industry as a whole is going to have to deliver. For the suggestion box, it would also be great if we could reconsider Web SQL and make file storage universal. Thanks, industry!

But can’t you do this already with JS?!

Yeah, kind of. There will be multiple platforms from which you can deliver mobile and web. C++ all the things. Ruby for everybody. Dart, I guess. It’s more about the organization of everything. JS frameworks (React, NativeScript, whatever) are generally going to be web-focused. Flutter in its own way is a reaction to React, but this isn’t a JS or Flutter rant, so we’ll move on.

In a bit.

Am I anti-Javascript? Yes. Kind of. It’s a single-threaded, typeless, no-consequences world because of decisions a handful of people made in the mid-90s. I also like it sometimes too. What I really dislike is the default position that everything needs to be Javascript. It doesn’t. Assuming WebAssembly works out, it’ll be interesting to see what impact that has⁵.

We (Touchlab) just see this next wave of technologies as a better answer for a lot of scenarios. Especially if you’re a large org doing a lot of Java (and there are a lot of those). Outside of just this stack, the more similar web and mobile become, the less different everything needs to be (architecturally speaking, of course).

For now, you can definitely do Android and iOS. Those implementations will be able to talk to Kotlin/Native. See here. Everything kind of works together.

So, anyway. Keeping an eye out for that multiplatform commit…


¹ So, my UI rant. The short version is, most of the cross-platform stuff is trying to be an “everything” solution. Architecture and UI. Most include some way of interacting with “native” bits, but they’re generally treated very much as an exception. That means you need to make Big Decisions about platform choice. I like little decisions. What to do about more common UI is something we should look at, but the foundations should be poured first.

²There are some concepts to unpack here. J2objc is not something most iOS devs have been excited about largely because it feels kind of like a hand-me-down from the Android side. React Native and everything else that’s JS-based is a hand-me-down from the web. Xamarin, well, you’re either an MS shop or you’re not. I think the iOS community would embrace Kotlin more, largely because there’s going to be a need for iOS-leaning libraries, and until somebody builds a viable Swift for Android, it’s the best opportunity to *not* be in a hand-me-down situation. Mobile teams need a response when management says “what about ____?”, and this is a good one.

³ Don’t get too tripped up on the details. You could write a book on that. I don’t think the “server devs” should ship packages sdk’s to the “front end devs”. There’s a lot of history about how you should and should not do this. If you’re old enough, you’ll remember when Java Enterprise Bean spec tried to dictate separate roles for different parts of your team. Guess they still do? Amazing. Would not recommend. A good write up of implementing code sharing with different team focus can be found in the “Developing & Debugging” section of this blog post from Slack.

⁴ You could make it one big monolithic back-end service, but the mobile part still needs to get done right. Server architecture recommendations today tend to like a lot of little services, so that’s what we put in there, but you don’t *need* to do it that way.

⁵ i.e. What happens to JavaScript if you don’t need it for the web?

Q&A with Jeff and Kevin

Q&A with Jeff and Kevin

What’s the elevator pitch on Touchlab?

Touchlab is an enterprise-grade innovation advisory firm helping application development leaders identify and eliminate inefficiency to free-up resources for reinvestment into innovation sprints.

What’s the difference between Touchlab and bigger enterprise mobile development firms like Accenture, IBM? 

IBM and Accenture aren’t known for building successful startup products. They specialize in selling big contracts to big companies. The output? Big applications we’ve all seen before. Not true mobile innovation. Furthermore, they don’t specialize in code-sharing, which is the only true path to accelerating mobile innovation. Touchlab has built disruptive products for enterprises and startups and is a pioneer in code-sharing for enterprise environments.

Our expertise in code-sharing and our D.R.Y. philosophy is a strategic advantage.

How are code-sharing and cross-platform development different?

Cross Platform is a “Capital B BIG Decision.” You have to live with that decision and it’s not an easy separation. Code-Sharing is lower risk because you can start small and there is no lock-in.

One day, will every enterprise mobile development team be using code-sharing?

Yes! Backend architecture and logic doesn’t need to be developed natively. We believe the trend towards enterprise code-sharing will start there and spread to other areas with potential for standardization.