Recipes for Decoupling
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Recipes for Decoupling

About the Book

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"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 You can postpone this work for a bit, but eventually you'll have to catch up, or your project may end up hopelessly outdated.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

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    • Refactoring
    • PHP
    • Laravel
    • Symfony
    • Zend
    • Software Engineering
    • Automated Software Testing
    • Web Development
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About the Author

Matthias Noback
Matthias Noback

Matthias Noback has been building web applications since 2003. He is the author of Principles of Package Design and Object Design Style Guide and Advanced Web Application Architecture. He is a regular blogger, public speaker and trainer.

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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

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