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

Querying Repositories


Upon comparison, Repositories are different than a collection if we consider their querying ability. A Repository deals with a large set of objects that typically aren't in memory when the query is performed. It's not feasible to load all the instances of a Domain object in memory and perform a query over them.

A good solution is to pass a criterion and let the Repository handle the implementation details to successfully perform the operation. It might translate the criterion to SQL or ORM queries or iterate over an in-memory collection. However, it doesn't matter, because the implementation deals with it.

Specification Pattern

A common implementation for the criterion object is the Specification pattern. A specification is a simple predicate that takes a Domain object and returns a boolean. Given a Domain object, it will return true if it specifies the specification, and false otherwise:

interface PostSpecification
{
    /**
     * @return boolean
     */
    public function...