Articles

An Illustrated Guide to Covariance and Contravariance in Kotlin

Confused about generic subtyping? With just a few simple, foundational concepts, almost everything about variance becomes clear. If you're confused about how subtyping works with generics in Kotlin, start here.

Getting Real with Kotlin's Reified Type Parameters

Kotlin's reified type parameters give you the ability to do more with your generic type parameters than you normally could do, but there are also some important limitations to consider. In this article, we'll look at what they are, how they work, and why you want them in your tool belt.

When (and when not) to Use Type Parameter Constraints in Kotlin

Kotlin allows you to constrain a generic's type parameter to an upper bound class, limiting the range of types that it can accept. In this article, we'll explore why this can be a helpful tool in your toolbelt.

Choosing between with() and run()

The scope functions found in the Kotlin standard library include with() and run(), which work similarly. In this guide, we check out the similarities, and a few surprising differences that can help you decide when to use each.

Understanding Kotlin's let(), also(), run(), and apply()

Kotlin's standard library includes a handful of scope functions, like let(), also(), run(), and apply(). It's easy to confuse them, so this guide provides an easy-to-understand way to think about them, so that you can choose the right one for the job.