Babysteps to OCaml on iOS

Sean Grove
Sean GroveNov 18th, 2020

Early this morning I was able to get some very, very simple OCaml code running on my physical iPhone 6+, which was pretty exciting for me.

I had been excited about the idea since seeing a post on Hacker News. Reading through, I actually expected the whole process to be beyond-terrible, difficult, and buggy - to the point where I didn't even want to start on it. Luckily, Edgar Aroutiounian went well beyond the normal open-source author's limits and actually sat down with me and guided me through the process. Being in-person and able to quickly ask questions, explore ideas, and clear up confusion is so strikingly different to chatting over IRC/Slack. I'll write a bit more about the process later, but here's an example of the entire dev flow right now: edit OCaml (upper left), recompile and copy the object file, and hit play in XCode.


The next goal is to incorporate the code into this site's codebase, to build a native iOS app for this site as an example (open source) iOS client with a unikernel backend. I'm very eager to try to use ReactNative, for:

  1. The fantastic state models available (just missing a pure-OCaml version of DataScript)
  2. Code sharing between the ReactJS and ReactNative portions
  3. Hot-code loading
  4. Tons of great packages, like ReactMotion that just seem like a blast to play with


I'd really like to thank Edgar Aroutiounian and Gina Maini for helping me out, and for being so thoughtful about what's necessary to smooth out the rough (or dangerously sharp) edges in the OCaml world. Given that tooling is a multiplicative force to make devs more productive, I often complain about the lack of thoughtful, long-term investment in it. Edgar (not me!) is stepping up to the challenge and actually making very impressive progress on that front, both in terms of code and in documenting/blogging.

As a side note, he even has an example native OSX app built using OCaml, tallgeese.