Domain Modeling Made Functional

Chapter 10Implementation: Working with Errors

What happens if a product code is malformed, or a customer name is too long, or the address validation service times out? Any system will have errors, and how we handle them is important. Consistent and transparent error handling is critical to any kind of production-ready system.

In the previous chapter, we deliberately removed the error “effect” (the Result type) from the steps in the pipeline so that we could focus on composition and dependencies.

But this effect is important! In this chapter, we’ll restore the Result to the type signatures and learn how to work with them.

More generally, we’ll explore the functional approach to error handling, developing a technique that allows you to capture ...