Value Objects | Domain-Driven Design in PHP

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Domain-Driven Design in PHP

By : Keyvan Akbary, Carlos Buenosvinos, Christian Soronellas

4.3 (9)

Domain-Driven Design in PHP

4.3 (9)

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.

Preface

Preface

Who Should Read This Book

DDD and PHP Community

Summary of Chapters

Code and Examples

Free Chapter

Getting Started with Domain-Driven Design

Getting Started with Domain-Driven Design

Why Domain-Driven Design Matters

The Three Pillars of Domain-Driven Design

Considering Domain-Driven Design

The Tricky Parts

Strategical Overview

Related Movements: Microservices and Self-Contained Systems

Wrap-Up

Architectural Styles

Architectural Styles

The Good Old Days

Layered Architecture

Event Sourcing

Wrap-Up

Value Objects

Value Objects

Definition

Value Object vs. Entity

Currency and Money Example

Characteristics

Basic Types

Testing Value Objects

Persisting Value Objects

Security

Wrap-Up

Entities

Entities

Introduction

Objects Vs. Primitive Types

Identity Operation

Persisting Entities

Testing Entities

Validation

Entities and Domain Events

Wrap-Up

Services

Services

Application Services

Domain Services

Domain Services and Infrastructure Services

Testing Domain Services

Anemic Domain Models Vs Rich Domain Models

Wrap-Up

Domain-Events

Domain-Events

Introduction

Definition

Characteristics

Modeling Events

Doctrine Events

Persisting Domain Events

Publishing Events from the Domain Model

Spreading the news to Remote Bounded Contexts

Wrap-Up

Modules

Modules

General Overview

Leverage Modules in PHP

Bounded Contexts and Applications

Structuring Code in Modules

Wrap-Up

Aggregates

Aggregates

Introduction

Key Concepts

What Is an Aggregate?

Why Aggregates?

A Bit of History

Anatomy of an Aggregate

Aggregate Design Rules

Sample Application Service: User and Wishes

Transactions

Wrap Up

Factories

Factories

Factory Method on Aggregate Root

Factory on Service

Testing Factories

Wrap-Up

Repositories

Repositories

Definition

Repositories Are Not DAOs

Collection-Oriented Repositories

Persistence-Oriented Repository

Querying Repositories

Managing Transactions

Testing Repositories

Testing Your Services with In-Memory Implementations

Wrap-Up

Application

Application

Requests

Anatomy of an Application Service

Testing Application Services

Transactions

Security

Domain Events

Command Handlers

Wrap-Up

Integrating Bounded Contexts

Integrating Bounded Contexts

Integration Through the Data Store

Integration Relationships

Implementing Bounded Context Integrations

Wrap-Up

Hexagonal Architecture with PHP

Hexagonal Architecture with PHP

Introduction

First Approach

Repositories and the Persistence Edge

Decoupling Business and Persistence

Migrating our Persistence to Redis

Decouple Business and Web Framework

Rating an Idea Using the API

Console App Rating

Testing Rating an Idea UseCase

Testing Infrastructure

Arggg, So Many Dependencies!

Domain Services and Notification Hexagon Edge

Let's Recap

Hexagonal Architecture

Key Points

What's Next?

Bibliography

Bibliography

The End

The End

Characteristics

While modeling an Ubiquitous Language concept in code, you should always favor Value Objects over Entities. Value Objects are easier to create, test, use, and maintain.

Keeping this in mind, you can determine whether the concept in question can be modeled as a Value Object if:

It measures, quantifies, or describes a thing in the Domain
It can be kept immutable
It models a conceptual whole by composing related attributes as an integral unit
It can be compared with others through value equality
It is completely replaceable when the measurement or description changes
It supplies its collaborators with side-effect-free behavior

Measures, Quantifies, or Describes

As discussed before, a Value Object should not be considered just a thing in your Domain. As a value, it measures, quantifies, or describes a concept in the Domain.

In our example, the Currency object describes what type of Money it is. The Money object measures or quantifies units of a given currency.

Immutability

This is one of...

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