The Language Of Collections

Transcript

1. Exploring The Language Of Collections
2. twitter.com/tinydroptest2 github.com/turanct
3. engagor.github.io
4. Exploring The Language Of Collections
5. situation
6. you nd this in your codebase public function displayCoffeeRunsOpenForOrders() { $coffeeRuns = $this->coffeeRunsRepository->getAll(); $openForOrders = array(); foreach ($coffeeRuns as $coffeeRun) { if ($coffeeRun->ordersCanBeMade()) { $openForOrders[] = $coffeeRun; } } return $openForOrders; }
7. wait a minute
8. what if CoffeeRunsRepository contains 10 years worth of coffee runs
10. experiment 1: iterator
11. we had this public function displayCoffeeRunsOpenForOrders() { $coffeeRuns = $this->coffeeRunsRepository->getAll(); $openForOrders = array(); foreach ($coffeeRuns as $coffeeRun) { if ($coffeeRun->ordersCanBeMade()) { $openForOrders[] = $coffeeRun; } } return $openForOrders; }
12. Repository implements Iterator public function displayCoffeeRunsOpenForOrders() { $coffeeRuns = $this->coffeeRunsRepository; $openForOrders = array(); foreach ($coffeeRuns as $coffeeRun) { if ($coffeeRun->ordersCanBeMade()) { $openForOrders[] = $coffeeRun; } } return $openForOrders; }
13. memory problem solved* *depending on implementation
14. new problem created have a guess?
15. dependency injection public function __construct( CoffeeRunsRepository $coffeeRuns ) { $this->coffeeRuns = $coffeeRuns; } foreach ($this->coffeeRuns as $coffeeRun) { // ... }
16. we're using an undocumented interface
17. interface CoffeeRunsRepository { /** * @return CoffeeRun[] A list of CoffeeRuns */ public function getAll(); } make Repostory interface extend Iterator interface? typehint on Iterator instead of the repository?
19. experiment 2: classic refactor
20. we had this public function displayCoffeeRunsOpenForOrders() { $coffeeRuns = $this->coffeeRuns->getAll(); $openForOrders = array(); foreach ($coffeeRuns as $coffeeRun) { if ($coffeeRun->ordersCanBeMade()) { $openForOrders[] = $coffeeRun; } } return $openForOrders; }
21. we end up with this public function displayCoffeeRunsOpenForOrders() { return $this->coffeeRuns->openForOrders(); }
22. return coffee runs that are open for orders
23. interface changed interface CoffeeRunsRepository { // ... /** * @return CoffeeRun[] A list of CoffeeRuns open for orders */ public function openForOrders(); // ... }
24. wait a minute
25. what if we want to have runs open for orders happening before noon? our interface will grow and grow and grow
27. experiment 3: laravel collections
28. public function displayCoffeeRunsOpenForOrders() { $coffeeRuns = collect($this->coffeeRuns->getAll()); $openForOrders = $coffeeRuns->filter( function (CoffeeRun $run) { return $run->ordersCanBeMade(); } )->filter( function (CoffeeRun $run) { return $run->happensBeforeNoon(); } )->all(); return $openForOrders; } Eloquent always returns Collection s like this
29. methods for ltering declarative style memory preserving* *when using eloquent
30. unreadable mess jargon like filter
31. recap
32. not so nice: foreach over array Repository as an Iterator speci c ltering methods on Repository jargon
33. nice: abstraction encapsulation contracts declarative style language
34. experiment 4: language
35. coffee runs that are open for orders .
36. coffee runs that are open for orders and are happening before noon .
37. coffee runs -> that are ( open for orders )-> and are ( happening before noon );
38. interface CoffeeRuns { /** * @param callable function that takes a CoffeeRun * and returns a boolean * * @return CoffeeRuns that match the predicate */ public function thatAre(callable $matchingPredicate); /** * @return CoffeeRun[] An array of CoffeeRuns */ public function asArray(); }
39. public function displayCoffeeRunsOpenForOrders() { $coffeeRuns = $this->coffeeRuns->getAll(); $runsOpenForOrders = $coffeeRuns ->thatAre($openForOrders); return $runsOpenForOrders->asArray(); } public function displayCoffeeRunsBeforeNoonOpenForOrders() { $coffeeRuns = $this->coffeeRuns->getAll(); $runsOpenForOrders = $coffeeRuns ->thatAre($happeningBeforeNoon) ->thatAre($openForOrders); return $runsOpenForOrders->asArray(); }
40. domain language declarative style small interfaces combinations possible
41. wait a minute
42. what if we want to have MySQL WHERE statements? our closures will not suf ce
43. interface CoffeeRuns { /** * @param Predicate * * @return CoffeeRuns that match the predicate */ public function thatAre(Predicate $matching); /** * @return CoffeeRun[] An array of CoffeeRuns */ public function asArray(); } we could have Predicate objects that can be translated to a MySQL statement, or anything else
44. shut up and take my money
45. things to remember
46. language helped us understand
47. declarative style helped us understand
48. contracts* helped us understand *interfaces, a.o.
49. encapsulation helped us understand
50. questions?
51. twitter.com/tinydroptest2 github.com/turanct