author: Michał Powała
source repository: ddd-in-php

ddd-in-php

This repository is a study of a book Domain-Driven Design in PHP written by CARLOS BUENOSVINOS, CHRISTIAN SORONELLAS and KEYVAN AKBARY:

Book's code snip sets

Domain Driven Design In PHP code snip sets (GitHub)

Mentioned books (I decided to point out)

• Applying Domain Driven Design Patterns by Jimmy Nilsson
  
• Introducing Eventstorming by Alberto Brandolini
  
• NoSQL Distilled: A Brief Guide to the Emerging World of Polyglot Persistence by Pramod J. Sadalag
  
• Patterns of Enterprise Application Architecture by Martin Fowler
  
• Enterprise Integration Patterns by Gregor Hohpe and Bobby Woolf
  
• Building Microservices by Sam Newman

Entities and surrogate Id

User contains $userId, $email, $password

class DoctrineUser extends User
{
    private $surrogateUserId;
    
    public function __construct(UserId $userId, $email, $password) {
        parent::__construct($userId, $email, $password);
        $this->surrogateUserId = $user->id()
    }
}

Notes

• Doctrine is an implementation of a Data Mapper pattern
• I always wondered where validation (assertion) should lay - ASSERTION SHOULD BE ENCLOSED WITHIN PRIVATE SETTER (unless that small ValueObject - don't need setter imho, then)
• Public VS private constructor (named constructor):
  • public constructor: if object is created with all needed (necessary) properties provided from outside the class
  • private constructor and public static named constructor: if object is created without provided all necessary data (it generates it)
  • addictionally it allows (static constructor) to implement constructor method without throwing an event, and in business specific method that is named static constructor you can publish events
• If other bounded context generates ID, necessary is Event Driven architecture
• Constructing an object from plain data such as an array is called hydratation
• "Factories help us keeping the business invariants" [page 177] - read more about factories
• Command buses and message systems are used outside the domain model!!! Domain model only published events but all the rest is handled in app layer or infrastructure layer!
• "AsMartin Fowler said in the PoEAA book, the first law of distributed systems is always:Don’t distribute" ❤️
• on message subscribes run commands to the domain using CommandBus (message subscribers are on infrastructure)

TODO

• read more about streams
• read more about redis and elasticsearch
• read about surrogate properties in a context to database
• read about active records (don't like it, but still I need to know more)
• read about Data Mapper patter
• read about Unit of Work pattern
• read more about messaging (not publishing itself) events!
• read about invariants in context of aggregates
• read about database mechanism pessimistic and optimistic concurrency control
• read about data-structures, like Sets (repository is an implementation of set)
• read more about data transformers****
• read about aggregates and bounded contexts, how does two different aggregate roots within single context cooperate