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)

Applying constructor injection

Let's apply constructor injection to our ACME registration service. This time we will be refactoring the REST package, starting with the Register endpoint. You may remember that Register is one of three endpoints in our service, the others being Get and List.
The Register endpoint has three responsibilities:

  • Validate the registration is complete and valid
  • Call the currency conversion service to convert the registration price to the currency requested in the registration
  • Save the registration and the converted registration price into the database

The code for our Register endpoint currently looks as shown in the following code:

// RegisterHandler is the HTTP handler for the "Register" endpoint
// In this simplified example we are assuming all possible errors
// are user errors and returning "bad request" HTTP 400.
// There...