Summer Update

Hi there!

I'll be taking a month-long vacation starting this weekend (family road trip), and I wanted to drop a quick line before I head off, and give a status update on longevity.

First off, I made a video tutorial last week that's pretty nice. It's about 70 minutes, but it's probably a comfortable watch for most people at 1.5x speed.

I've been playing around with early steps in migrating to shapeless on a feature branch. The first bite I broke off for this is to rewrite my test data generation tools using Arbitrary from ScalaCheck. It's not finished yet, but I got through the most worrisome part, which was, how am I going to generate all the implicit stuff used by shapeless libraries? In this case, I need a bunch of implicits to generate an Arbitrary[P] using scalacheck-shapeless. The worrisome part is that I have to generate the class for a user-provided type P. This is problematic in general, because in order to get things like a Generic[P], you have to have the actual type P right there in your hands. Nothing else will do - not a TypeTag, nothing else along those lines. Thankfully, I already have macros that produce scaffolding around the type P, so I can generate the code to produce the Arbitrary[P], and it ends up getting inserted right there in the user code, where P is well known. I'm sure happy about that because it means the major worry I had about implementing things with shapeless is now solved.

So that's on a branch, and I put that aside because I decided I really need to start focusing in on providing users a schema migration tool. It's really the last "absolutely must have" feature for longevity, and while working on making longevity more functional is very enticing, I need to keep my priorities straight. The last two functionalization tasks - the ModelEv, PEv, and Key type classes, and the finally tagless, were both super important, but most importantly, user-facing changes. Most of the rest of the functionalization work I want to do is more internal, and shouldn't affect the user API too much. So I can definitely de-prioritize it. Only thing is, I want to support options in queries, and I've sort of been delaying that until after shapeless is in place. I could actually do it before then, but it just isn't the most efficient course, as I would have to rewrite most of it in shapeless.

So when I come back in September, I'll definitely be focusing on schema migration tool first. Once I have a rudimentary working tool out, I'll probably start splitting my time between that and migrating to shapeless.

Have a great August everybody!

Longevity Goes Finally Tagless

Longevity - your persistence framework for Scala and NoSQL - has always sported a future-based API. But now in release 0.24, longevity has gone finally tagless, replacing the hardcoded references to scala.concurrent.Future with a generic effect F. We currently support three effects: Scala futures, the cats-effect IO monad, and an old-fashioned blocking API for the purists out there. We plan to support a variety of Task monads as effects in the near future, and you can always write your own effect as well.

For more information on longevity effects, see the user manual.

For examples on how longevity works with different effects, check out this demo code.

This release is exciting for me for many reasons. Perhaps most importantly, longevity now sports a truly functional API with support for IO monads. But the flexibility of the finally tagless approach is truly freeing. We can satisfy the purist functional programmers, and continue to support people who want to do reactive programming with futures, with a minimum of cognitive overhead. It's also exciting to me because it's a major step on my personal path to becoming a better functional programmer.

But the best part for me is just how beautiful the repository API has become. Just look at it. In a sense, this is how this API was always meant to be. Perfectly intuitive, fully typesafe, just the right level of abstraction without a hint of leaks. I couldn't imagine doing persistence in Scala any other way.