Domain-Driven Design: da curiosidade à prática
6º meetup da comunidade PHP Pernambuco
Luciano Queiroz
Senior PHP Software Engineer @ LPCDev
Backend Engineer @ Hello Fresh
Motivação
Brasil????
Agenda
- Strategic Design
- Bounded Contexts / Ubiquitous Language
- Event Storming
- Tactical Design
- Architecture
- Domain Blocks
- Event Sourcing
O que é DDD?
Problem Space
Solution Space
O que é DDD?
"DDD é um conjunto de ferramentas que te auxiliam a entregar softwares de alto valor: estrategicamente e tecnicamente."
Vaughn Vernon - Domain-Driven Design Distilled
Domain-Driven design
1
Software é interpretado como centro de custo e não investimento.
2
O banco e modelagem de dados é muito priorizado ao invés das operações e processos do domínio.
"Businesses regularly put too much effort into developing glorified database table editors."
Vaughn Vernon - Implementing Domain-Driven Design
3
Desenvolvedores muito apegados a ferramentas e tecnologias para resolver problemas.
You're allowed and encouraged to use third party libraries, as long as you put them together yourself without relying on a framework or microframework to do it for you. An effective developer knows what to build and what to reuse, but also how his/her tools work. Be prepared to answer some questions about those libraries, like why you chose them and what other alternatives you're familiar with.
4
Estimativas são muito valorizadas, e criar estimativas leva tempo e energia, resultando em delay nas entregas. Desenvolvedores para atender as estimativas desenvolvem uma "Big ball of mud", porque não tem tempo/liberdade/conhecimento para modelar um software que reflete exatamente como o domínio funciona.
5
Baixa colaboração entre stakeholders e developers, resultando em muita tradução entre o que o stakeholder pensa e o código que o desenolvedor escreve.
Strategic Design
Como levar um motorista de um ponto ao outro no menor tempo possível?
Navigation
Destination
Origin
Route
Driver
Navigation
Destination
Origin
Route
Driver
Car
Plate
Alerts
Navigation
Destination
Origin
Route
Driver
Car
Plate
Alert
Collaborator
Location
Score
Rides
Navigation
Destination
Origin
Route
Alert
Collaborator
Location
Score
Driver
Car
Plate
RideAvailability
Commutation
Rider
Commutation
Commutation
Why not... Car rental?
Navigation
Destination
Origin
Route
Alert
Collaborator
Location
Score
Driver
Car
Plate
RideAvailability
Commutation
Rider
Commutation
Commutation
Rental
CarRentAvailability
Car
Duration
Total
Price
Renter
Commutation
Rental
Bounded Contexts
NavigationContext
RentalContext
CollaborationContext
CarPoolContext
Navigation
Routes
Destination
Origin
ETA
ETA
Commutation
Car
Rental
Price
Duration
Renter
CarOwner
SeatsAvailable
CarCapacity
Rider
Driver
Driver
Collaborator
Editor
Alert
Location
Car
Identifying the core domain
What's the core domain of the previous domain model?
NavigationContext
RentalContext
CollaborationContext
CarPoolContext
Navigation
Routes
Destination
Origin
ETA
ETA
Commutation
Car
Rental
Price
Duration
Renter
CarOwner
SeatsAvailable
CarCapacity
Rider
Driver
Driver
Collaborator
Editor
Alert
Location
Car
NavigationContext
RentalContext
CollaborationContext
CarPoolContext
Navigation
Routes
Destination
Origin
ETA
ETA
Commutation
Car
Rental
Price
Duration
Renter
CarOwner
SeatsAvailable
CarCapacity
Rider
Driver
Driver
Collaborator
Editor
Alert
Location
Car
Sub Domains
NavigationContext
RentalContext
CollaborationContext
CarPoolContext
Navigation
Routes
Destination
Origin
ETA
ETA
Commutation
Car
Rental
Price
Duration
Renter
CarOwner
SeatsAvailable
CarCapacity
Rider
Driver
Driver
Collaborator
Editor
Alert
Location
Car
Generic Domain
NavigationContext
RentalContext
CollaborationContext
CarPoolContext
Navigation
Routes
Destination
Origin
ETA
ETA
Commutation
Car
Rental
Price
Duration
Renter
CarOwner
SeatsAvailable
CarCapacity
Rider
Driver
Driver
Collaborator
Editor
Alert
Location
Car
Event Storming
Tactical Design
Architecture
Driver
Car (n)
Profile
Plate
Entities
<?php
declare(strict_types=1);
namespace RecipeApi\Domain;
use Prooph\EventSourcing\AggregateRoot;
class Driver extends AggregateRoot
{
private $driverId;
private $cars = [];
private $email;
public static function new(
DriverId $driverId,
Email $email
) : self {
$self = new self();
$self->recordThat(DriverWasRegistered::fromRequestData($recipeId, $email));
return $self;
}
public function aggregateId(): RecipeId
{
return $this->driverId;
}
public function cars(): array
{
return $this->cars;
}
public function whenDriverWasRegistered(DriverWasRegistered $event)
{
$this->driverId = DriverId::fromString($event->aggregateId());
$this->email = $event->email();
}
public function addCar(Car $car)
{
$this->recordThat(CarWasAdded::fromRequestData($this->driverId, $car));
}
public function whenCarWasAdded(CarWasAdded $event)
{
$this->cars[] = $event->car();
}
}Value Object
<?php
use Rhumsaa\Uuid\Uuid;
final class DriverId
{
private $uuid;
private function __construct(Uuid $uuid)
{
$this->uuid = $uuid;
}
public static function new(): self
{
return new self(Uuid::uuid4());
}
public static function fromString(string $uuid): self
{
return new self(Uuid::fromString($uuid));
}
public function __toString(): string
{
return (string) $this->uuid;
}
public function uuid(): Uuid
{
return $this->uuid;
}
}Event Sourcing
DriverWasCreated
2 CarWasAdded
1 CarWasRemoved
DriverWasCreated
1 CarWasAdded