Book Image

Domain-Driven Design in PHP

By : Keyvan Akbary, Carlos Buenosvinos, Christian Soronellas
Book Image

Domain-Driven Design in PHP

By: Keyvan Akbary, Carlos Buenosvinos, Christian Soronellas

Overview of this book

Domain-Driven Design (DDD) has arrived in the PHP community, but for all the talk, there is very little real code. Without being in a training session and with no PHP real examples, learning DDD can be challenging. This book changes all that. It details how to implement tactical DDD patterns and gives full examples of topics such as integrating Bounded Contexts with REST, and DDD messaging strategies. In this book, the authors show you, with tons of details and examples, how to properly design Entities, Value Objects, Services, Domain Events, Aggregates, Factories, Repositories, Services, and Application Services with PHP. They show how to apply Hexagonal Architecture within your application whether you use an open source framework or your own.
Table of Contents (24 chapters)
Title Page
Credits
Foreword
About the Authors
Acknowledgments
www.PacktPub.com
Customer Feedback
Dedication
Preface
14
Bibliography
15
The End

Validation


Validation is a highly important process in our Domain Model. It checks not only for the correctness of attributes, but also for that of entire objects and the composition of those objects. Different levels of validation are required in order to keep this Model in a valid state. Just because an object consists of valid attributes (on a per basis) doesn't necessarily mean the object (as a whole) is valid. And the opposite is true: valid objects don't necessarily equal valid compositions.

Attribute Validation

Some people understand validation as the process whereby a service validates the state of a given object. In this case, the validation conforms to a Design-by-contract approach, which consists of preconditions, postconditions, and invariants. One such way to protect a single attribute is by using Chapter 3Value Objects. In order to make our design more flexible for change, we focus only on asserting Domain preconditions that must be met. Here, we'll be using guards as an easy...