A couple of years ago, I wrote that The Builder pattern is a finite state machine!. A state machine consists of states and transitions between them. As a developer, I want to make illegal states unrepresentable, i.e., users of my API can’t create non-existent transitions. My hypothesis is that only a static typing system allows this at compile-time. Dynamic typing systems rely on runtime validation. In this blog post, I will show that it holds true, with a caveat.

A derived attribute is an attribute computed from other attributes e.g.: The fullName is aggregated from the first, middle and last nameThe age is computed from the birthdateetc. Kotlin offers different options to manage such derived attributes. Let’s browse through them.

It seems pretty popular right now to bash widespread software design practices, e.g. dependency injection, frameworks, annotations, etc. While there are some downsides of adopting those practices, I believe there are more benefits. In that post, I’d like to address those points, and come up with arguments in favor.

When Java came out some decades ago, it was pretty innovative at the time. In particular, its exception handling mechanism was a great improvement over previous C/C++. For example, in order to read from the file, there could be a lot of exceptions happening: the file can be absent, it can be read-only, etc.