Closing keynote, as presented at Codemotion 2014, LaraconEU 2014, Redevelop 2014, CodeConnexx 2013 and PHP North East 2014. This presentation makes a reference to a reading list I received. For those interested, the release consists of most of the general classics, such as Gang Of Four "Design Patterns", The Pragmatic Programmer, Structure and Interpretation of Computer Programs, Domain Driven Design and a few others. The actual list remains tucked away in a box somewhere.

1. Surgeon General's Warning
This talk is clocked at 1 slide per 12.8 seconds and features unsafe
amounts of code. Presenter is a registered Class 3 Fast Talker (equal
to 1 Gilmore Girls episode).
Viewing is not recommended for those hungover, expected to become
hungover or consuming excessive amounts of caffeine. Do not watch
and operate motor vehicles.
If you accidentally consume this talk, flush brain with kitten pictures
and seek emergency help in another talk. No hard feelings, seriously.
It's almost the weekend, after all. Why are we even here?
Notice in accordance with the PHP Disarmament Compact of 1992. Void where prohibited.

2. Models & Service Layers
Hemoglobin & Hobgoblins
DrupalCon Amsterdam
Ross Tuck

3. Freerange Codemonkey
Know-It-All
Hot-Air Balloon

4. @rosstuck
rosstuck.com

5. About Today

6. Hemoglobin

7. Anemia.

9. Objects can too.

10. Model
class TodoList {
function setName($name);
function getName();
function setStatus($status);
function getStatus();
function addTask($task);
function setTasks($tasks);
function getTasks();
}

11. array(
'name' => '',
'status' => '',
'tasks' => ''
);
Model

12. Bad ThingTM

13. “In essence the problem with anemic domain
models is that they incur all of the costs of a
domain model, without yielding any of the
benefits.”
-Martin Fowler

14. Our industry standard i s a n a n t i p a t t ern.

15. Ouch.

16. Important Note

20. Models
Stuf

21. Integration over implementation

22. Our Setup

23. Model
class TodoList {
function setName($name);
function getName();
function setStatus($status);
function getStatus();
function addTask($task);
function setTasks($tasks);
function getTasks();
}

24. Model
class Task {
function setDescription($desc);
function getDescription();
function setPriority($priority);
function getPriority();
}

25. An ORM that's not Doctrine 2.
A framework that's not Symfony2.
I promise.

26. CRUD

27. Controller
function addTaskAction($req) {
$task = new Task();
$task->setDescription($req->get('desc'));
$task->setPriority($req->get('priority'));
$list = $this->todoRepo->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
return $this->redirect('edit_page');
}

29. Controller
function addTaskAction($req) {
$task = new Task();
$task->setDescription($req->get('desc'));
$task->setPriority($req->get('priority'));
$list = $this->todoRepo->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
return $this->redirect('edit_page');
}

30. Anemic Model
Hard to Maintain
Testability
SRP wha?

31. In Defense Of CRUD.
No, seriously.

32. Low Barrier to Entry.

33. Easy to follow.
If you can keep it
in your head.

34. Sometimes it really is just data entry.
(but it usually isn't)
(but sometimes it is)

35. Not entirely a technical issue.

36. Service Layer

37. • Service Layer
• Service Container
• Web Service
• Service Oriented Architecture
• Domain Service
• Stateless Service
• Software-as-a-service
• Platform-as-a-service
• Whatever-as-a-service meme
• Delivery Service
• Laundry Service

38. Application Service

40. Model
Controller
View

41. Model
Service Layer
Controller
View

42. Why?

44. 1) Multiple User Interfaces
Web + REST API
+ CLI
+ Workers

45. 2) “In between” Logic

46. 3) Decouple from frameworks

47. Model
Service Layer
Controller
View

48. Just Build The Stupid Thing

49. Service
Layer

50. Controller
function addTaskAction($req) {
$task = new Task();
$task->setDescription($req->get('desc'));
$task->setPriority($req->get('priority'));
$list = $this->todoRepo->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
return $this->redirect('edit_page');
}

51. Service
class TodoService {
function addTask(TodoList $list, $desc, $priority) {
$task = new Task();
$task->setDescription($desc);
$task->setPriority($priority);
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

52. Service
class TodoService {
function findById($id) {
return $this->repository->findById($id);
}
}

53. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
}

54. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($id, $desc, $priority) {
$list = $this->todoService->findById($id);
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask($list, $desc, $priority);

55. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
function addTaskCommand($id, $desc, $priority) {
$list = $this->todoService->findById($id);
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask($list, $desc, $priority);
CLI

56. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($id, $desc, $priority) {
$list = $this->todoService->findById($id);
if (!$list) { throw new NotFoundException(); }
$this->todoService->addTask($list, $desc, $priority);

57. Service
class TodoService {
function findById($id) {
return $this->repository->findById($id);
}
}

58. Service
class TodoService {
function findById($id) {
$todo = $this->repository->findById($id);
if (!$todo) {
throw new TodoNotFoundException();
}
return $todo;
}
}
not http exception

59. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($id, $desc, $priority) {
$list = $this->todoService->findById($id);
$this->todoService->addTask($list, $desc, $priority);

60. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($id, $desc, $priority) {
$list = $this->todoService->findById($id);
$this->todoService->addTask($list, $desc, $priority);

61. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($name, $desc, $priority) {
$list = $this->todoService->findByName($name);
$this->todoService->addTask($list, $desc, $priority);

63. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($name, $desc, $priority) {
$list = $this->todoService->findByName($name);
$this->todoService->addTask($list, $desc, $priority);

64. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($name, $desc, $priority) {
$list = $this->todoService->findByName($name);
$this->todoService->addTask($list, $desc, $priority);

65. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
CLI
function addTaskCommand($name, $desc, $priority) {
$listId = $this->todoService->findIdByName($name);
$this->todoService->addTask($listId, $desc, $priority);

66. Service
class TodoService {
public function findLatestLists() {
return $this->repository->findLatestLists();
}
}

67. Service
class TodoService {
public function findLatestLists() {
if ($this->cache->has('latest:lists')) {
return $this->cache->get('latest:lists');
}
$results = $this->repository->findLatestLists();
$this->cache->set('latest:lists', $results);
return $results;
}
}

68. Indirect Advantages

69. Readability

70. Junior Protection

71. Discoverability

72. Service
class TodoService {
function findById($id);
function addTask($todo, $desc, $priority);
function prance();
}

73. Mission Accomplished

74. Model
class TodoList {
function setName($name);
function getName();
function setStatus($status);
function getStatus();
function setTasks($tasks);
function getTasks();
}

75. Dumb as a box of rocks.

76. Model
class TodoList {
function setName($name);
function getName();
function setStatus($status);
function getStatus();
function setTasks($tasks);
function getTasks();
}
Where's mah logic?

77. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$task = new Task();
$task->setDescription($desc);
$task->setPriority($priority);
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

79. “Organizes business logic by procedures
where each procedure handles a single
request from the presentation.”
-Fowler

80. Transaction Scripts

81. Simple

82. More flexible
Than CRUD,
at least

83. Don't scale quite as well

84. What does belong in a service layer?

85. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$task = new Task();
$task->setDescription($desc);
$task->setPriority($priority);
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

86. Orchestration

87. Transactions
Security
Notifications
Bulk operations

88. Facade

89. Fat Model, Skinny Controller

90. Fat Model, Skinny Service Layer

91. (re)Thinking

92. addTask()
findById()
findLatestLists()
Service
write
read
read

93. Remodeling our Reading
by
Refactoring our Repository
Redux

94. Service
class TodoService {
function findById($id) {
$todo = $this->repository->findById($id);
if (!$todo) {
throw new TodoNotFoundException();
}
return $todo;
}
}

95. Repository
interface TodoRepository {
public function findById($id);
public function findLatestLists();
}

96. Repository
class TodoDbRepository implements TodoRepository {
public function findById($id) {
$todo = $this->db->select(...);
if (!$todo) {
throw new TodoNotFoundException();
}
return $todo;
}
}

97. Repository
class TodoDbRepository implements TodoRepository {
public function findById($id) {
$todo = $this->db->select(...);
if (!$todo) {
throw new TodoNotFoundException();
}
return $todo;
}
}
raw db connection

98. Repository
class TodoDbRepository implements TodoRepository {
public function findById($id) {
$todo = $this->repository->find($id);
if (!$todo) {
throw new TodoNotFoundException();
}
return $todo;
}
}
FIXED

99. Repository
interface TodoRepository {
public function findById($id);
public function findLatestLists();
}

100. Repository
interface EntityRepository {
public function createQueryBuilder($alias);
public function createResultSetMappingBuilder($alias);
public function createNamedQuery($queryName);
public function createNativeNamedQuery($queryName);
public function clear();
public function find($id, $lockMode, $lockVersion);
public function findAll();
public function findBy($criteria, $orderBy, $limit, $offset);
public function findOneBy($criteria, $orderBy);
public function __call($method, $arguments);
public function getClassName();
public function matching(Criteria $criteria);
}

101. Repository
interface TodoRepository {
public function findById($id);
public function findLatestLists();
}

102. Service
class TodoService {
function findById($id) {
$todo = $this->repository->findById($id);
if (!$todo) {
throw new TodoNotFoundException();
}
return $todo;
}
}

103. Service
class TodoService {
function findById($id) {
return $this->repository->findById($id);
}
}

104. Service
class TodoService {
public function findLatestLists() {
if ($this->cache->has('latest:lists')) {
return $this->cache->get('latest:lists');
}
$results = $this->repository->findLatestLists();
$this->cache->set('latest:lists', $results);
return $results;
}
}

105. Repository
class TodoDbRepository implements TodoRepository {
public function findLatestLists() {
if ($this->cache->has('latest:lists')) {
return $this->cache->get('latest:lists');
}
$results = $this->repository->query(...);
$this->cache->set('latest:lists', $results);
return $results;
}
}

106. Repository Decorator Decorator object
class CachingTodoRepository implements TodoRepository {
public function findLatestLists() {
if ($this->cache->has('latest:lists')) {
return $this->cache->get('latest:lists');
}
$results = $this->innerRepository->findLatestLists();
$this->cache->set('latest:lists', $results);
return $results;
}
}
TodoDbRepository

107. DI Layer
new TodoService(
new CachingTodoRepository(
new TodoDbRepository(
$entityManager->getRepository('TodoList')
)
)
)

108. The Inverse Biggie Law

109. Mo' classes
Mo' decoupling and reduced overall design issues

110. Too many finder methods?

111. Controller
$this->todoService->matching(array(
new ListIsClosedCriteria(),
new HighPriorityCriteria()
));

112. DoctrineCriteria

113. Interlude: Services here...
...services there...
...services everywhere!

114. TaskService
Task
TodoListService
TodoList
TagService
Tag
TaskRepository TodoListRepository TagRepository

117. TaskService
Task
TodoListService
TodoList
TagService
Tag
TaskRepository TodoListRepository TagRepository

119. Task
TodoService
TodoList
Tag

120. Task
UserService
TodoService
TodoList
Tag
User

122. Task
TodoService
TodoList
Tag
UserService
User

123. Service
class TodoListService {
public function findByUser(User $user) {
return $this->repository->findByUser($user);
}
}

124. Service
class TodoListService {
public function findByUser(User $user) {
return $user->getTodoLists();
}
}

125. Task
TodoService
TodoList
Tag
Interfaces!
UserService
User

126. Services aren't only for entities

127. Scale can differ wildly

128. PrintingService

129. Quality of Implementation

130. (re)Modeling our Writing

131. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$task = new Task();
$task->setDescription($desc);
$task->setPriority($priority);
$task->setTodoList($list);
$this->repository->save($task);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

132. Model
class TodoList {
function addTask(Task $task) {
$this->tasks[] = $task;
}
}

133. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task();
$task->setDescription($desc);
$task->setPriority($priority);
$this->tasks[] = $task;
}
}

134. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task($desc, $priority);
$this->tasks[] = $task;
}
}

135. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
}
}
ORM allowance

136. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task($desc, $priority);
$this->tasks[] = $task;
}
}

137. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

138. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task($desc, $priority);
$this->tasks[] = $task;
}
}

139. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task($desc, $priority);
$this->tasks[] = $task;
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
}
}
}

140. Meaningful Tests

141. Working Together

142. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

143. Model
class TodoList {
function addTask($desc, $priority) {
$task = new Task($desc, $priority);
$this->tasks[] = $task;
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
}
}
}

144. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

145. class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
if (count($this->tasks) > 10) {
$this->auditLog->logTooAmbitious($task);
$this->mailer->sendMessage('Too unrealistic');
}
Service

146. class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
if (count($this->tasks) > 10) {
$this->auditLog->logTooAmbitious($task);
$this->mailer->sendMessage('Too unrealistic');
}
Service

147. TodoService
PrintingService

148. Something new...

149. Something better...

150. Domain Events

151. Common Pattern

152. Observer

153. New usage

154. Model
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
$this->raise(
new TaskAddedEvent($this->id, $desc, $priority)
);
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
}
}

155. Event
class TaskAddedEvent {
protected $description;
protected $priority;
function __construct($desc, $priority) {
$this->description = $desc;
$this->priority = $priority;
}
}

156. Model
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
$this->raise(
new TaskAddedEvent($this->id, $desc, $priority)
);
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
}
}

157. Model
class TodoList {
protected $pendingEvents = array();
protected function raise($event) {
$this->pendingEvents[] = $event;
}
public function releaseEvents() {
$events = $this->pendingEvents;
$this->pendingEvents = array();
return $events;
}
}
Excellent Trait

158. No dispatcher

159. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$this->auditLog->logNewTask($task);
$this->mailer->sendMessage('New thingy!');
}
}

160. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
}
}

161. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
$list->addTask($desc, $priority);
$this->repository->save($list);
$events = $list->releaseEvents();
$this->eventDispatcher->dispatch($events);
}
}

162. Event Listeners
class EmailListener {
function onTaskAdded($event) {
$taskDesc = $event->getDescription();
$this->mailer->sendMessage('New thingy: '.$taskDesc);
}
function onUserRegistered($event) {
$this->mailer->sendMessage('welcome sucka!');
}
}

163. Model
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
$this->raise(
new TaskAddedEvent($this->id, $desc, $priority)
);
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
}
}

164. Model
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
$this->raise(
new TaskAddedEvent($this->id, $desc, $priority)
);
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
$this->raise(new WasTooAmbitiousEvent($this->id));
}
}

165. Nice things:

166. Model
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
$this->raise(
new TaskAddedEvent($this->id, $desc, $priority)
);
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
$this->raise(new WasTooAmbitiousEvent($this->id));
}
}
Logic is here!

167. Service
class TodoListService {
protected $dependency1;
protected $dependency2;
protected $dependency3;
protected $dependency4;
protected $dependency5;
protected $dependency6;
}
Big ball of mud
in the making

168. Event Listeners
class EmailListener {
function onTaskAdded($event) {
$taskName = $event->task->getName();
$this->mailer->sendMessage('New thingy: '.$taskName);
}
function onUserRegistered($event) {
$this->mailer->sendMessage('welcome sucka!');
}
}
Thin. Easy to test

169. TodoService
Serialize & Send,
Sucka!
PrintingService

170. Model
function addTask($desc, $priority) {
$task = new Task($desc, $priority, $this);
$this->tasks[] = $task;
$this->raise(
new TaskAddedEvent($this->id, $desc, $priority)
);
if (count($this->tasks) > 10) {
$this->status = static::UNREALISTIC;
}
}

171. Less nice things.

172. Humans hate debugging events.
Dev Logging.
Debug commands.

173. Model
Service Layer
Controller
View

174. Model
Service Layer
Controller
View

175. Model
Service Layer
Controller
View

176. Consuming Application Services

177. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
}

178. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$this->todoService->addTask(
$list, $req->get('desc'), $req->get('priority')
);
return $this->redirect('edit_page');
}

179. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$list->addTask($req->get('desc'), $req->get('priority'));
return $this->redirect('edit_page');
}

180. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$list->addTask($req->get('desc'), $req->get('priority'));
$list->rename('blah');
return $this->redirect('edit_page');
}

181. Controller
function addTaskAction($req) {
$list = $this->todoService->findById($req->get('id'));
$list->addTask($req->get('desc'), $req->get('priority'));
$list->rename('blah');
$this->todoService->addTask(...);
return $this->redirect('edit_page');
}

183. Model
Service Layer
Controller
View

184. Model
Service Layer
Controller
View

185. Model
Service Layer
Controller
View

187. View Models

188. PHP version, not MVVM.

189. Service
class TodoService {
function findById($id) {
$todoList = $this->repository->findById($id);
return $todoList;
}
}

190. Service
class TodoService {
function findById($id) {
$todoList = $this->repository->findById($id);
return new TodoDTO($todoList);
}
}

191. TodoDTO
class TodoDTO {
public function getName();
public function getStatus();
public function getMostRecentTask();
}

193. Service
class TodoService {
function generateReport() {
$data = $this->repository->performSomeCrazyQuery();
return new AnnualGoalReport($data);
}
}

194. Ain't rocket science.

195. Reverse it: DTOs not for output...

196. ...but for input.

197. Going Commando

200. Command
class AddTaskCommand {
public $description;
public $priority;
public $todoListId;
}

201. Controller
function addTaskAction($req) {
$command = new AddTaskCommand();
$command->description = $req->get('description');
$command->priority = $req->get('priority');
$command->todoListId = $req->get('todo_id');
$this->todoService->execute($command);
return $this->redirect('edit_page');
}
}

202. Handler Foo
Controller Service Handler Bar
Handler Baz

203. Controller Service
Handler Baz

204. Service
class TodoListService {
}

205. Service
class TodoListService {
function addTask(TodoList $list, $desc, $priority) {
}
}

206. Service
class TodoListService {
function execute($command) {
}
}

207. Service
class TodoListService {
function execute($command) {
get_class($command);
}
}

208. Service
class TodoListService {
function execute($command) {
$command->getName();
}
}

209. Service
class TodoListService {
function execute($command) {
$command->execute();
}
}

210. Service
class TodoListService {
function execute($command) {
}
}

211. What goes in a handler?

212. Handler
class TodoListHandler {
function handleAddTask($cmd) {
$list = $this->repository->findById($cmd->todoListId);
$list->addTask($cmd->description, $cmd->priority);
}
function handleCompleteTask($command)
function handleRemoveTask($command)
}

213. Service
class TodoListService {
function execute($command) {
}
}

214. Service
class CommandBus {
function execute($command) {
}
}

215. Service
class MyCommandBus implements CommandBus {
function execute($command) {
}
}

216. Service
class LazyLoadingCommandBus implements CommandBus {
function execute($command) {
}
}

217. Service
class ValidatingCommandBus implements CommandBus {
function execute($command) {
if (!$this->validator->isValid($command)) {
throw new InvalidCommandException();
}
$this->innerCommandBus->execute($command);
}
}

218. Command
class AddTaskCommand {
public $description;
public $priority;
public $todoListId;
}

219. Command
use SymfonyComponentValidatorConstraints as Assert;
class AddTaskCommand {
/** @AssertLength(max="50") */
public $description;
public $priority;
public $todoListId;
}

220. Logging
Transactions
Event Dispatching

221. Command

222. Fewer Dependencies per class.
Simple layers.
Easy to test.

223. View Models + Commands

224. Model
Service Layer
Commands ViewModels
Controller
View

225. forms
templates
validators
CRUD for the framework.
Domain Model for the chewy center.
tough logic
semantics
testing

226. Diverge Further

227. CQRS

228. On the surface, it looks the same.

229. Controller
function addTaskAction($req) {
$command = new AddTaskCommand();
$command->description = $req->get('description');
$command->priority = $req->get('priority');
$command->todoListId = $req->get('todo_id');
$this->commandBus->execute($command);
return $this->redirect('edit_page');
}
}

230. CQS

231. Commands = Change Data
Queries = Read Data

232. CQRS

233. Model
class TodoList {
function rename($name);
function addTask($desc, $priority);
function getName();
function getTasks();
}

234. Two Models

235. Write Model
class TodoListModel {
function rename($name);
function addTask($desc, $priority);
}
Read Model
class TodoListView {
function getName();
function getTasks();
}

237. Model
class TodoList {
function rename($name);
function addTask($desc, $priority);
function getName();
function getTasks();
function getParticipatingUsers();
}

238. Write Model
class TodoListModel {
function rename($name);
function addTask($desc, $priority);
}
Read Model
class TodoListView {
function getName();
function getTasks();
function getParticipatingUsers();
}

239. Write Model
class TodoListModel {
function rename($name);
function addTask($desc, $priority);
}
Read Model
class TodoListView {
function getName();
function getTasks();
function getParticipatingUsers();
}
ORM entity
SQL query

240. Read and Write are two different systems.

241. User and Shopping Cart?

242. Same kind of split.

243. Surrounding classes?

244. A lot of it looks the same.

245. Handler
class TodoListHandler {
function handleAddTask($cmd) {
$list = $this->repository->findById($cmd->todoListId);
$list->addTask($cmd->description, $cmd->priority);
}
}

246. Service
class TodoListService {
public function findByUser(User $user) {
return $this->repository->findByUser($user);
}
}

247. Handler
class TodoListHandler {
Service
class TodoListService {
public function findByUser(User $user) {
return $this->repository->findByUser($user);
}
}
function handleAddTask($cmd) {
$list = $this->repository->findById($cmd->todoListId);
$list->addTask($cmd->description, $cmd->priority);
}
}

249. $todoList = new TodoList();
$this->repository->save($todoList);
$todoList->getId();
Controller

250. $command = new CreateTodoCommand(UUID::create());
$commandBus->execute($command);
$command->uuid;
Controller

251. Zoom Out

252. Martin Fowler
waz here

257. Domain
events

258. DB Views

259. Big
Honking
Queue

260. github.com/beberlei/litecqrs-php/
github.com/qandidate-labs/broadway
github.com/gregoryyoung/m-r

261. Pros & Cons

262. Big mental leap.
Usually more LOC.
Not for every domain.
Can be mixed.

263. Easy to Scale.
Bears Complexity.
Async Operations.
Event Sourcing.

264. Event Sourcing?

265. CQRS
+
Event Sourcing

266. Instead of storing the current state in the db...

267. ...store the domain events?

268. Snapshots
Debugging
Audit Log
Business Intelligence
Online/Offline users

269. Google it.
Or ask me afterwards.

270. Epilogue

271. "A foolish consistency is the hobgoblin of
little minds."
- Ralph Waldo Emerson

272. Strong opinions, weakly held.

273. Strong techniques, weakly held.

274. PHP 3

275. PHP 4 -5

276. PHP 5.3+

277. PHP 7

278. Might seem crazy.

279. Bang for the buck.

280. People ARE doing this.

281. It IS working for them.

282. You can too.

283. Questions?

284. Further Reading
• codebetter.com/gregyoung
• martinfowler.com/tags/domain driven design.html
• shawnmc.cool/domain-driven-design
• whitewashing.de
• verraes.net

285. Thanks To:
• Warnar Boekkooi @boekkooi
• Daan van Renterghem @DRvanR
• Matthijs van den Bos @matthijsvandenb

286. Image Credits
• http://www.flickr.com/photos/calgaryreviews/6427412605/sizes/l/
• http://msnbcmedia.msn.com/j/MSNBC/Components/Slideshows/_production/twisp_090511_
/twisp_090511_02.ss_full.jpg
• http://shotthroughawindow.wordpress.com/2011/07/22/hp7b/
• http://www.sxc.hu/photo/605471
• http://martinfowler.com/bliki/images/cqrs/cqrs.png
• http://www.flickr.com/photos/83346641@N00/5578975430/in/photolist-9uZH2y-8rTZL1-di
xjR-ffBPiv-8SbK8K-ffS4md-6UeEGP
• http://www.flickr.com/photos/lac-bac/7195938394/sizes/o/
• http://tdzdaily.org/wp-content/uploads/2013/03/Dumb-and-Dumber.png
• http://upload.wikimedia.org/wikipedia/commons/1/17/Charlton_Heston_in_The_Ten_Comm
andments_film_trailer.jpg
• http://commons.wikimedia.org/wiki/File:Trench_construction_diagram_1914.png
• http://www.flickr.com/photos/jeffreyww/4747314852/sizes/l/
• http://www.flickr.com/photos/jdhancock/3540861791/sizes/l/
• http://www.flickr.com/photos/superfantastic/50088733/sizes/l

287. joind.in/11986
Ross Tuck rosstuck.com
@rosstuck