5. Do you DDD?
• Domain Model
• Repository
• Ubiquitous language
• Domain Service
• Application Service
• Bounded context
• Context map
• Domain Event
• Anti Corruption Layer
• And many more…
6. class Product {
!
protected $title;
!
protected $price;
!
public function setPrice($price) {
// ..
}
!
public function getPrice() {
// ..
}
!
public function setTitle($title) {
// ..
}
!
public function getTitle() {
// ..
}
!
}
Is this your domain model?
7. class ProductController {
!
public function addToBasketAction($product) {
if ($product->getInStock() <= 0) {
$this->redirect();
}
!
// Add to basket
}
}
Where's your business logic?
9. Models, Views and Controllers
• Domain models grow into huge classes
• Hard to reason about (mental model)
• Domain models and relations are designed for viewing purposes
• Everything is extremely coupled
• “Big ball of mud”
Package: My.Shop
20. So what is a domain event?
• It’s a message …
• .. implemented as a class
• .. published to “the world”
• It’s past tense (e.g. OrderCompletedEvent)
• It’s transactionally coupled to your domain model
• It’s asynchronous
22. class Order {
!
public function complete() {
$this->completedAt = new DateTime();
!
$this->eventService->publish(
new OrderCompletedEvent(…)
);
}
!
}
Publishing event
25. 1. Customer places order
2. Signal / Slot trigger a foreign context to
send the order confirmation via email
3. Something breaks during persistence of the order.
What now?
Signal / Slot example
26. START TRANSACTION!
UPDATE order …
INSERT INTO event_store …
COMMIT!
!
!
If this succeeds the event is published to the message bus
Transactionally safe domain events
29. Benefits of using domain events
• Allows you to integrate bounded contexts with minimal
coupling and dependencies.
• Add features to the system with no changes to existing code.
• Get a more responsive system since a lot of functionality
is handled asynchronous.
• Get a more robust system. Easier to build fault tolerant system.
(Fx. problems with third party services like payment gateways etc.)
34. What is a bounded context?
Package?!
Subdirectory?!
Its own Flow installation?!
Another system?
Could be any of above as long as they are independent
and only integrate through domain events (or service calls).
!
No sharing of domain models etc.
35. How do I get started?
https://github.com/agitso/event
• Uses Doctrine’s PostFlush event listener to hook into
Doctrine after persistence and handle domain events.
• The same technique is used in Famly, where we have
currently handled +500.000 domain events
36. Recap
• Split your system into smaller modules / bounded contexts
• Put your business logic into the domain models
• Integrate modules with Domain Events (use application service calls
for synchronous interactions).
• Use controllers to orchestrate the views - that is fetch data
from Application Services and assign to views and similar.
NO BUSINESS LOGIC HERE.
