Why setters are bad

Inspired by "Implementing DDD" some examples why setters are bad and how you can avoid these - Internal tech-talk at move:elevator

Transcript

1. Tommy Mühle | tommy-muehle.io Why setters are bad 1
2. Tommy Mühle | tommy-muehle.io They have no context 2
3. Tommy Mühle | tommy-muehle.io Objects are not immutable 3 *Depends on the context
4. Tommy Mühle | tommy-muehle.io Common used anti patterns 4
5. Tommy Mühle | tommy-muehle.io Setter for everything 5
6. Tommy Mühle | tommy-muehle.io 6 class Article { private $state = 'unknown'; // ... public function setState($state) { if ($state === 'unknown') { // ... } $this->state = $state; } }
7. Tommy Mühle | tommy-muehle.io Use business relevant method names 7
8. Tommy Mühle | tommy-muehle.io 8 class Article { private $state = 'unknown'; // ... public function publish() { $this->state = 'published'; } }
9. Tommy Mühle | tommy-muehle.io Concrete business endpoints 9
10. Tommy Mühle | tommy-muehle.io 10
11. Tommy Mühle | tommy-muehle.io 10
12. Tommy Mühle | tommy-muehle.io 11
13. Tommy Mühle | tommy-muehle.io Use named constructors for objects in special state 12
14. Tommy Mühle | tommy-muehle.io 13 class Article { private $title; private $state; // ... public static function draft($title) { $article = new self(); $article->state = 'draft'; $article->title = $title; return $article; } }
15. Tommy Mühle | tommy-muehle.io Boolean flags 14
16. Tommy Mühle | tommy-muehle.io 15 class Article { private $deleted = false; // ... public function setDeleted($deleted) { $this->deleted = (bool) $deleted; } // ... } Boolean flag parameters
17. Tommy Mühle | tommy-muehle.io 16 Avoid boolean parameters class Article { private $deleted = false; // ... public function delete() { $this->deleted = true; } // ... }
18. Tommy Mühle | tommy-muehle.io Setter-Injection 17
19. Tommy Mühle | tommy-muehle.io 18 Avoid setter injection class MyService { private $logger; // ... public function setLogger($logger) { $this->logger = $logger; } }
20. Tommy Mühle | tommy-muehle.io 19 Avoid unnecessary conditions class MyService { private $logger; // ... public function myMethod(array $parameters) { // ... if ($this->logger instanceof LoggerInterface) { $this->logger->log('...'); } } }
21. Tommy Mühle | tommy-muehle.io Use constructor arguments instead 20
22. Tommy Mühle | tommy-muehle.io 21 class MyService { private $logger; // ... public function __construct($logger) { $this->logger = $logger; } } Make immutable objects
23. Tommy Mühle | tommy-muehle.io Special cases 22
24. Tommy Mühle | tommy-muehle.io Symfony forms 23
25. Tommy Mühle | tommy-muehle.io Use DataMappers 24
26. Tommy Mühle | tommy-muehle.io Decouple form from entity 25
27. Tommy Mühle | tommy-muehle.io Further cases … 26
28. Tommy Mühle | tommy-muehle.io Summary 27
29. Tommy Mühle | tommy-muehle.io Try to avoid setters anytime 28
30. Questions?
31. Thank you! Slides http:/ /bit.ly/2pTywBB @tommy_muehle