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)

Advantages of method injection

As we saw in the previous section, method injection is used extensively in the standard library. It is also extremely useful when you want to write your own shared libraries or frameworks. Its usefulness does not stop there.

It is excellent with functions—Everybody loves a good function, particularly those that follow the Single responsibility principle section, as discussed in Chapter 2, SOLID Design Principles for Go. They're simple, stateless, and can be highly reusable. Adding method injection to a function will increase its reusability by converting the dependency into an abstraction. Consider the following HTTP handler:

func HandlerV1(response http.ResponseWriter, request *http.Request) {
garfield := &Animal{
Type: "Cat",
Name: "Garfield",
}

// encode as JSON and output
encoder := json.NewEncoder...