Advanced

Changing the input or output of an API endpoint that is consumed by your front end, changing a field in a database that is coupled to a field in a model in our application. Sometimes, you see yourself making changes in two different systems and it’s really tempting to coordinate the release of both systems to keep them in sync.

So, you’re using an Object Relational Mapper of any kind and you have to, let’s say, remove a field from one of your models. This is a breaking change, as your contract with the database is going to break. If you have a small project that you can just take down for every release, that’s not a big deal, but:

One of the fantastic things about functional programming is that you have to abstract away the path that took you to the data, mostly with data structures. So when you are processing the some state of an Option, you know that the object is there. When processing the right of an Either, you know you have an object that has dodged every error or alternative path. You don’t get his benefit for free, as the data structure forces you to handle all of its states, you might see yourself needing three objects, all of them contained in their own instance of such a structure.