Book Image

Hands-On Dependency Injection in Go

By : Corey Scott
Book Image

Hands-On Dependency Injection in Go

By: Corey Scott

Overview of this book

Hands-On Dependency Injection in Go takes you on a journey, teaching you about refactoring existing code to adopt dependency injection (DI) using various methods available in Go. Of the six methods introduced in this book, some are conventional, such as constructor or method injection, and some unconventional, such as just-in-time or config injection. Each method is explained in detail, focusing on their strengths and weaknesses, and is followed with a step-by-step example of how to apply it. With plenty of examples, you will learn how to leverage DI to transform code into something simple and flexible. You will also discover how to generate and leverage the dependency graph to spot and eliminate issues. Throughout the book, you will learn to leverage DI in combination with test stubs and mocks to test otherwise tricky or impossible scenarios. Hands-On Dependency Injection in Go takes a pragmatic approach and focuses heavily on the code, user experience, and how to achieve long-term benefits through incremental changes. By the end of this book, you will have produced clean code that’s easy to test.
Table of Contents (15 chapters)

Chapter 6, Dependency Injection with Constructor Injection

1. What are the steps we used to adopt constructor injection?

  1. We identified the dependency we wanted to extract and eventually inject.
  2. We removed the creation of that dependency and promoted it to a member variable.
  3. We then defined the abstraction of the dependency as a local interface and changed the member variable to use that instead of the real dependency.
  4. We then added a constructor with the abstraction of the dependency as a parameter so that we could ensure the dependency was always available.

2. What is a guard clause and when would you use it?

We defined guard clauses as a piece of code the ensured the dependency was supplied (in other words, not nil). In some cases, we used them in our constructors so that we could be 100% sure the dependency was provided.


3. How does constructor injection affect the...