Recipes for Decoupling
by：Matthias Noback
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Book Description
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About the Book
Looking for a print edition? It’s available on Lulu.
“Future me will appreciate it if I apply even just half of the recipes in this fantastic book. I learnt something new from every chapter and I can’t wait to share some of these methods with my teams.” Andrew Barlow
“Another excellent book from Matthias Noback! I learned a lot about techniques how to decouple your application from frameworks, test suites and other libraries. And the best part: it showed me how to unleash the power of PHPStan with custom rules to make sure you stay decoupled.” Stefan Blanke
Software is never done. The world around your program changes faster than you want it to. Frameworks and libraries are abandoned and replaced with something better (or just something new), so you need to migrate. You can postpone this work for a bit, but eventually you’ll have to catch up, or your project may end up hopelessly outdated. I’m sure you know one or two of those projects!
How can you make all of this easier for yourself and the future maintainers of the project? The keyword is “decoupling”. You can change the design of your code to defend it against changes in any dependency your project relies on. Decoupling your code is a way to make it future-proof (without doing too much work that “you ain’t gonna need”).
About 10 years ago I started looking for ways to decouple my code, but at first I struggled to do it effectively. My code was decoupled in the wrong places, or in the wrong way. I got a better view on this topic after several intense experiences with some legacy projects, a big framework migration, and a complete project rewrite (that I’m sure could have been prevented). I’ve collected many recipes for decoupling along the way. This book gives you a practical overview of common situations that suffer from an often unintended high level of coupling in web applications. Of course, it also gives you step-by-step recipes to improve these situations. The examples in this book show you how to decouple from your web framework, templating engine, test framework, ORM, and so on.
Decoupling is one thing, but staying decoupled is something else entirely. That’s why in this book we focus on how to solidify the decoupling rules with PHPStan, the automated static analysis tool for PHP. That way we don’t have to rely on discipline and code reviews, but can let a tool point out possible coupling mistakes.
“Have you ever wondered how to efficiently decouple from your PHP framework? And how to enforce it through tooling? I did! And Recipes For Decoupling delivered me very well thought out explanations, examples and snippets for decoupling. It even explains step by step how to enforce these decoupling rules through PHPStan rules. The book contains examples from a variety of popular PHP frameworks including Symfony, Laravel, Mockery and PHPUnit.” – Vincent Hagen
“‘Decoupling’ is a delightful read that merits a slow read because you will want to stop and code after every chapter! Noback’s clarity and honesty is welcome in an era of big personalities, as is his ability to distill framework concepts to elegant code.” – Matthew Gatner
Table of Contents
Introduction
Coupling, Why is it Bad?
Decoupling, How to Do it Efficiently?
Objection
What’s Special About This Book?
How to Stay Decoupled?
Who Should Read This Book?
Overview of the Contents
About the Author
Changelog
10 May 2022
17 May 2022
26 May 2022
31 May 2022
7 June 2022
15 June 2022
29 June 2022
1 Creating Custom Rules for PHPStan
Introduction
Analyzing Code with PHPStan
Catching Specific Node Types
Adding Automated Tests for a PHPStan Rule
Deriving Types from the Current Scope
Putting a Node in Context
Generalizing a Rule
Conclusion
2 Web Frameworks
Introduction
Controllers
Show How the Response is Created
Only Use Constructor Injection for Dependencies
Make Every Step Explicit
Controllers Have No Parent Class
Every Action Has its Own Controller Class
Should We Use an HTTP Abstraction Library?
Rules for Decoupled Controllers
Forbidden Parent Classes
Allowing Only Parameters of a Certain Type
Enforcing Return Types
One Action Per Controller
Views
Pass All the Data That the Template Needs
Don’t Pass Objects That Don’t Belong in a Template
Rules for Decoupled Views
Don’t Use Certain Global Variables in a Template
Don’t Use Certain Functions in a Template
Don’t Pass Entities to a Template
Conclusion
3 CLI Frameworks
Introduction
Input
Collect Input First
Jump to a Service
Output
Using an Observer for Showing Output
Generalizing the Solution with Event Dispatching
Turn the Command Class Itself Into an Event Subscriber
Controllers Should Call Framework-agnostic Services
Rules for Decoupling
Use InputInterface and OutputInterface Only in Command Classes
4 Form Validation
Introduction
Form Validation
Protecting Data Inside the Model
Delegating Protection to Value Objects
Removing Duplicate Validation Logic
Defining an Explicit Shape for the Input Data
Rules for Decoupling
Don’t Pass a Single Array of Data to create()
Enforcing the Use of Closure-based Form Validation
Conclusion
5 ORMs and the Database
Introduction
Repository: an Abstraction for Persistence
Trying an Alternative Implementation
Application-generated IDs
PHPStan Rule: Disallow Auto-incrementing Model IDs
Defining Our Own Object API
Custom Mapping Code
PHPStan Rule: Only Allow Calls to fromDatabaseRecord() from Repository Classes
No Magic Persistence of Related Objects
Using Aggregate Design Rules
Limiting Changes to One Entity
Introducing View Models
Provide Read Models When the Framework Needs Your Data
Use Domain Events Instead of Persistence Events
PHPStan Rule: Forbidden Parameter Types
Conclusion
6 Test Frameworks
Introduction
Use Only the Most Basic Features of a Test Framework
Declare Test Dependencies Explicitly
PHPStan Rule: Don’t Allow PHPUnit Extensions
PHPStan Rule: Don’t Allow Class-level Set-up and Tear-down Functions
Assertions
Write Tests in Plain Code
Handwritten Test Doubles
PHPStan Rule: Don’t Generate Mocks
Conclusion
7 Conclusion
8 The End of the Book
