A survival guide to the Either monad in Scala
I started to work with Scala few months ago. One of the concepts that I had the most difficulties to understand is the Either monad. So, I decided to play around with it and better understand its power.
In this story I share what I’ve learned, hoping to help coders approaching this beautiful language.
The Either monad
Either is one of the most useful monads in Scala. If you are wondering what a monad is, well… I cannot go into the details here, maybe in a future story!
Imagine Either like a box containing a computation. You work inside this box, until you decide to get the result out of it.
In this specific case, our Either box can have two “forms”. It can be (either) a Left or a Right, depending on the result of the computation inside it.
I can hear you asking: “OK, and what is it useful for?”
The usual answer is: error handling.
We can put a computation in the Either, and make it a Left in case of errors, or a Right containing a result in case of success. The use of Left for errors, and Right for success is a convention. Let’s understand this with some code!
