Longevity Release 0.23 - Use Type Classes to Improve Type Safety of Persistent API

This longevity release has been a long time in the making. The main improvement here, and the one that has taken by far the most effort, is instituting the use of type classes to provide type safety for the persistence API. I've done a technical writeup on this work in my previous blog post. It's actually pretty interesting because I've never seen type classes quite this way before, so I think it's worth the read. The TLDR is that the repository API is now fully type safe, and the last instance of forcing users to inherit from a longevity trait has been removed.

Here are some of the other major improvements in this release:


An Interesting Use for Type Classes in Scala

This is a technical writeup of the major new feature in the longevity 0.23 release.

There are more than enough writeups on using type classes in Scala already. I normally wouldn't bother to write about it, but I will now, for three reasons. First, the usage of type classes in longevity seems unique to me; I haven't seen type classes used quite this way before. Second, I want to write this up as documentation for any future contributors to the longevity project. Third, I'd really like to get your feedback into what I've done here, and hear your advice about how I might further improve on things.


Longevity now has Better Support for Alternative JDBC Back Ends

Longevity release 0.21 features a new back end called JDBC. It should work in a lot of situations where using SQLite back end with a non-SQLite driver would fail. There is also a much easier development path for creating your own back end, should the generic JDBC back end not be sufficient.


Ten Ways You Can Contribute To An Open Source Project

Okay, so it's really about my open source project. But that's the whole point. I don't want it to be my project. I want it to be your project too! While this article is written to specifically address contributing to longevity, much of the material here will probably apply to other projects as well.

This is a complete rewrite of the contributing page on the longevity web site. You can read it over there if you like. I've also pasted the contents below for your convenience:


New SQLite Back End for Longevity

Longevity release 0.20.0 is out, featuring the following changes:

  • Added a SQLite back end.
  • Trying to be a bit more formal, changed occurrences of "Mongo" with "MongoDB" in the public API.
  • Replaced "partition key" terminology with "primary key". I was undecided about this for a long time leading up to implementing the feature, and I think I made the wrong choice when the time came. "Partition key" is a little over specified for distributed database scenario. It's a little more general to posit that a database table can have multiple keys, but can more powerfully optimize a single one of those keys at your choosing. Now that I have three very different back ends, it's getting harder and harder to overfit longevity to a single database technology!

Keep reading to learn more about the new back end: