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)

Disadvantages of JIT injection

While JIT injection can be handy, it cannot be used in all scenarios, and there are a few gotchas to be wary of. These include the following:

Can only be applied to static dependencies—The first and perhaps most significant disadvantage is that this method can only be applied to dependencies that only change during testing. We cannot use it to replace parameter injection or config injection. This is caused by the fact that dependency instantiation happens inside a private method and only on the first attempt to access the variable.

Dependency and user life cycles are not separated—When using constructor injection or parameter injection, it's often safe to assume the dependency being injected is fully initialized and ready for use. Any costs or delays, like those related to creating resource pools or preloading data, will have already...