![class AccountsController
{
public function index()
{
$accounts = Account::all();
return View::make(‘accounts.index’, [
‘accounts’ => $accounts
]);
}
}](https://image.slidesharecdn.com/domaindrivendesign-140917103913-phpapp02/85/Introduction-to-Domain-driven-design-LaravelBA-5-24-320.jpg)
![class AccountsController
{
public function index()
{
$accounts = Account::all();
return View::make(‘accounts.index’, [
‘accounts’ => $accounts
]);
}
}](https://image.slidesharecdn.com/domaindrivendesign-140917103913-phpapp02/85/Introduction-to-Domain-driven-design-LaravelBA-5-25-320.jpg)
Introduction to Domain driven design (LaravelBA #5)
- 3. Ubiquitous Language That’s all there is to it
- 4. Ubiquitous Language That’s all there is to it Questions?
- 5. Client (Domain expert) Project Manager Developer We need to add a new security policy to our accounts. Our customers can’t have more than two active offers per billing term. We need to restrict promotions. A user cannot have more than two promotions per month. public function validate(User $user) { // … other crazy validations if (count ($user->getPromotions()) > 2) throw new ValidationException( “User can’t have more than 2 promotions per month” ); // … continue with crazy validations }
- 6. Favor model language over translations
- 7. Client (Domain expert) Project Manager Developer We need to add a new security policy to our accounts. Our customers can’t have more than two active offers per billing term. public function validate(Account $account) { // … other crazy validations if (! $account->satisfies( new ActiveOffersPerBillingTermSecurityPolicy )) throw new ValidationException( “Account did not satisfy the active offers security policy” ); // … continue with crazy validations }
- 8. ActiveOffersPerBillingTerm SecurityPolicy … really? TOO MUCH CODE! I WON’T TYPE THAT!!!11
- 9. Semantics
- 10. Semantics ActiveOffersPerBillingTermSecurityPolicy means something in the MODEL LANGUAGE count($user->getPromotions()) > 2 does not convey this knowledge
- 11. Semantics ActiveOffersPerBillingTermSecurityPolicy means something in the MODEL LANGUAGE count($user->getPromotions()) > 2 does not convey this knowledge => MAKE IMPLICIT BUSINESS RULES EXPLICIT
- 12. Favor model language over translations When a domain expert (client) feels something’s wrong with the model language, you’ll know something’s wrong with the domain model.
- 13. Client (Domain expert) Project Manager Developer When we talk about a billing term, we need to consider if the customer is billed on a monthly or yearly basis. | class ActiveOffersPerBillingTermSecurityPolicy | { | protected $maxOffers = 2; | | public function isSatisfiedBy(Account $account) | { | return count( - | $account->getMonthlyOffers() + | $account->getOffersForBillingTerm() | ) < $this->maxOffers; | }
- 14. Domain Knowledge
- 15. Domain Knowledge Focus your efforts in building a clear domain, specific to your client’s needs
- 17. Client (Domain expert) class LongOverdueCustomerContactCommand { public function execute() { $customers = Customer::where( ‘account.balance’, ‘<’, 0 )->get(); foreach ($customers as $customer) $this->sendRefinanceEmail($customer); } } Project Manager Developer We need to contact long overdue customers to refinance their debt.
- 18. Client (Domain expert) class LongOverdueCustomerContactCommand { public function execute() { $customers = Customer::where( ‘account.balance’, ‘<’, 0 )->get(); foreach ($customers as $customer) $this->sendRefinanceEmail($customer); } } Project Manager Developer We need to contact long overdue customers to refinance their debt.
- 19. Client (Domain expert) Project Manager Developer We need to contact long overdue customers to refinance their debt. What is the difference between a regular customer, an overdue customer and a long overdue customer?
- 20. Client (Domain expert) class CustomerRepository { public function findOverdue() { return Customer::where(‘account.balance’, ‘<’, 0) ->get(); } public function findLongOverdue() { // Write more complex query logic for this one... } } Project Manager Developer Overdue is straightforward, customers in debt right now. Long overdue customers are the ones that have been overdue over the last 3 billing terms, at the end of each billing term.
- 21. Knowledge crunching Knowledge crunching deepens the domain model, and brings better understanding
- 22. But… How?
- 24. class AccountsController { public function index() { $accounts = Account::all(); return View::make(‘accounts.index’, [ ‘accounts’ => $accounts ]); } }
- 25. class AccountsController { public function index() { $accounts = Account::all(); return View::make(‘accounts.index’, [ ‘accounts’ => $accounts ]); } }
- 27. Entities
- 28. Entities Objects with an identity Lifespan Unique criteria
- 29. ValueObjects
- 30. ValueObjects Defined by their attributes
- 31. Aggregates
- 32. Aggregates Cluster of domain objects Transactional coherence
- 33. Services
- 34. Services Domain coordinators Define actions
- 35. Repositories
- 36. Repositories Data access abstraction
- 37. Factories
- 39. Domain Events
- 40. Domain Events Objects that represent significant domain events
- 46. Domain-oriented Architecture Isolate your domain model from specific application needs: UI - Persistence - External Services - Application workflow - etc...
- 47. So… What’s the point?
- 48. It’s not about writing code
- 49. It’s not about writing code That’s the easy part… right?
- 50. It’s not about writing code It’s about understanding what needs to be solved before starting to code
- 51. Creating a language which makes conversations between domain experts and developers possible without misinterpretations
- 52. Creating a language which makes conversations between domain experts and developers possible without (so many) misinterpretations
- 53. ● Eric Evans, “Domain-Driven Design: Tackling Complexity in the Heart of Software” ● Vaughn Vernon, “Implementing Domain-Driven Design” ● Martin Fowler, “Patterns of Enterprise Application Architecture” ● dddcommunity.org | Domain Driven Design Community ● -http://domainlanguage.com/ddd/reference/DDD_Reference_2011-01-31.pdf ● -http://www.lmgtfy.com/?q=Domain+Driven+Design