Book Image

Get Your Hands Dirty on Clean Architecture

By : Tom Hombergs
Book Image

Get Your Hands Dirty on Clean Architecture

By: Tom Hombergs

Overview of this book

Building for maintainability is key to keeping development costs low and processes easy. The second edition of Get Your Hands Dirty on Clean Architecture is here to equip you with the essential skills and knowledge to build maintainable software. With this comprehensive guide, you’ll explore the drawbacks of conventional layered architecture and the advantages of domain-centric styles such as Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture. Then, you’ll dive into hands-on explanations on how to convert hexagonal architecture into actual code. You'll learn in detail about different mapping strategies between the layers of hexagonal architecture and discover how to assemble the architectural elements into an application. Additionally, you’ll understand how to enforce architecture boundaries, which shortcuts produce what types of technical debt, and how, sometimes, it is a good idea to willingly take on those debts. By the end of this second edition, you'll be armed with a deep understanding of the hexagonal architecture style and be ready to create maintainable web applications that save money and time.
Table of Contents (13 chapters)

A Use Case in a Nutshell

First, let's discuss what a use case actually does. Usually, it follows these steps:

  1. Takes input
  2. Validates business rules
  3. Manipulates the model state
  4. Returns output

A use case takes input from an incoming adapter. You might wonder why I didn't call this step "Validate input." The answer is that I believe use case code should care about the domain logic and we shouldn't pollute it with input validation. So, we will do input validation somewhere else, as we will see shortly.

The use case is, however, responsible for validating business rules. It shares this responsibility with the domain entities. We will discuss the distinction between input validation and business rule validation later in this chapter.

If the business rules were satisfied, the use case then manipulates the state of the model in one way or another, based on the input. Usually, it will change the state of a domain object and pass this new state to a port implemented...