Autowiring

When learning modern PHP frameworks, the term autowiring crops up quite a bit. In this talk we will explore what autowiring is and how its used. We will look at the mechanics of a framework such as DI, Factories and DIC before looking at how autowiring fits in and how it really works.

Transcript

1. Autowiring Mike Oram • Mayden Academy Lead @MPOram
2. About me Full-stack developer PHP and JavaScript I run Mayden Academy Learn new stuff and teach it to people @MPOram
3. @MPOram
4. @MPOram
6. Autowiring @MPOram
8. First things first 1. Dependency Injection 2. Factories 3. Dependency Injection Containers 4. Autowiring @MPOram
9. Dependency Injection @MPOram
10. Dependency Injection NOT DEPENDENCY INVERSION @MPOram
13. Postcard @MPOram class UserModel { private $db; private $logger; public function __construct() { $this->db = new PDO('mysql:host=127...','user','pass'); $this->logger = new Logger('logs/error.log'); } }
14. Letter & Envelope class UserModel { private PDO $db; private Logger $logger; public function __construct(PDO $db, Logger $logger) { $this->db = $db; $this->logger = $logger; } } @MPOram
15. Without Dependency Injection $userModel = new UserModel(); With Dependency Injection $db = new PDO('mysql:host=127...','user','pass'); $logger = new Logger('logs/error.log'); $userModel = new UserModel($db, $logger); @MPOram
16. Dependency Injection Pros: • Decouples your dependencies - easier to switch out objects @MPOram
17. Dependency Injection Pros: • Decouples your dependencies - easier to switch out objects • Makes code unit testable - mock dependant objects @MPOram
18. Dependency Injection Pros: • Decouples your dependencies - easier to switch out objects • Makes code unit testable - mock dependant objects Cons: • Have to know the class dependencies - more effort, less encapsulation @MPOram
19. Dependency Injection Pros: • Decouples your dependencies - easier to switch out objects • Makes code unit testable - mock dependant objects Cons: • Have to know the class dependencies - more effort, less encapsulation • Learning curve @MPOram
20. Dependency Injection Pros: • Decouples your dependencies - easier to switch out objects • Makes code unit testable - mock dependant objects Cons: • Have to know the class dependencies - more effort, less encapsulation • Learning curve @MPOram
21. Factories @MPOram
22. Factories class UserModel { private PDO $db; private Logger $logger; public function __construct(PDO $db, Logger $logger) { $this->db = $db; $this->logger = $logger; } } @MPOram
23. Factories @MPOram function UserModelFactory { $db = new PDO('mysql:host=127...','user','pass'); $logger = new Logger('logs/error.log'); $userModel = new UserModel($db, $logger); return $userModel; }
24. Factories @MPOram function UserModelFactory { $db = new PDO('mysql:host=127...','user','pass'); $logger = new Logger('logs/error.log'); $userModel = new UserModel($db, $logger); return $userModel; } $userModel = UserModelFactory();
25. Factories Pros: • Removes the need to know dependencies - encapsulation @MPOram
26. Factories Pros: • Removes the need to know dependencies - encapsulation • Reduces code duplication - DRY @MPOram
27. Factories Pros: • Removes the need to know dependencies - encapsulation • Reduces code duplication - DRY Cons: • Breaks dependency injection - Create duplicate instances of a class @MPOram
28. Factories Pros: • Removes the need to know dependencies - encapsulation • Reduces code duplication - DRY Cons: • Breaks dependency injection - Create duplicate instances of a class • Have to know/look if a class has a factory or not @MPOram
29. Dependency Injection Container @MPOram
30. Dependency Injection Container @MPOram $container = new \App\Container(); $container['db'] = new PDO('mysql:host=127...','user','pass'); $container['Logger'] = new Logger('logs/error.log');
31. Dependency Injection Container @MPOram $container = new \App\Container(); $container['db'] = new PDO('mysql:host=127...','user','pass'); $container['Logger'] = new Logger('logs/error.log'); $container['UserModel'] = function ($container) { $db = $container->get('db'); $logger = $container->get('logger'); $userModel = new UserModel($db, $logger); return $userModel; };
32. Dependency Injection Container @MPOram $container = new \App\Container(); $container['db'] = new PDO('mysql:host=127...','user','pass'); $container['Logger'] = new Logger('logs/error.log'); $container['UserModel'] = new UserModelFactory();
33. Dependency Injection Container @MPOram $container = new \App\Container(); $container['db'] = new PDO('mysql:host=127...','user','pass'); $container['Logger'] = new Logger('logs/error.log'); $container['UserModel'] = new UserModelFactory(); // elsewhere in your application $userModel = $container->get('UserModel');
34. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation @MPOram
35. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation • Removes the need to know if a class has a factory @MPOram
36. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation • Removes the need to know if a class has a factory • Reduces code duplication - DRY @MPOram
37. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation • Removes the need to know if a class has a factory • Reduces code duplication - DRY • Only one instance of each class @MPOram
38. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation • Removes the need to know if a class has a factory • Reduces code duplication - DRY • Only one instance of each class • Centralises object creation @MPOram
39. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation • Removes the need to know if a class has a factory • Reduces code duplication - DRY • Only one instance of each class • Centralises object creation Cons: • Can be unnecessarily complex @MPOram
40. Dependency Injection Container Pros: • Removes the need to know dependencies - encapsulation • Removes the need to know if a class has a factory • Reduces code duplication - DRY • Only one instance of each class • Centralises object creation Cons: • Can be unnecessarily complex • Requires a lot of code and setup @MPOram
41. Okay but… what is autowiring?! 1. Dependency Injection 2. Factories 3. Dependency Injection Containers 4. Autowiring @MPOram
42. “The ability of the container to automatically create and inject dependencies” @MPOram
43. A DIC that can construct classes with dependencies without a factory @MPOram
44. Autowiring @MPOram class UserModel { private PDO $db; private Logger $logger; public function __construct(PDO $db, Logger $logger) { $this->db = $db; $this->logger = $logger; } }
45. class UserModel { private PDO $db; private Logger $logger; public function __construct(PDO $db, Logger $logger) { $this->db = $db; $this->logger = $logger; } } Autowiring @MPOram
46. class UserModel { private PDO $db; private Logger $logger; public function __construct(PDO $db, Logger $logger) { $this->db = $db; $this->logger = $logger; } } $userModel = $container->get('UserModel'); Autowiring @MPOram
47. Autowiring @MPOram Pros: • No factories
48. Autowiring @MPOram Pros: • No factories • No DIC configuration
49. Autowiring @MPOram Pros: • No factories • No DIC configuration • Easy to use
50. Autowiring Pros: • No factories • No DIC configuration • Easy to use • Multi-stage dependency resolution @MPOram
51. class UserController { private UserModel $model; public function __construct(UserModel $model) { $this->model = $model; } } $userController = $container->get('UserController'); Autowiring @MPOram
52. $userController = $container->get('UserController'); $db = new PDO('mysql:host=127...','user','pass'); $logger = new Logger('logs/error.log'); Autowiring @MPOram
53. $userController = $container->get('UserController'); $db = new PDO('mysql:host=127...','user','pass'); $logger = new Logger('logs/error.log'); $userModel = new UserModel($db, $logger); Autowiring @MPOram
54. $userController = $container->get('UserController'); $db = new PDO('mysql:host=127...','user','pass'); $logger = new Logger('logs/error.log'); $userModel = new UserModel($db, $logger); $userController = new UserController($userModel); Autowiring @MPOram
55. Autowiring Pros: • No factories • No DIC configuration • Easy to use • Multi-stage dependency resolution @MPOram
56. Autowiring Cons: • Black Magic @MPOram Pros: • No factories • No DIC configuration • Easy to use • Multi-stage dependency resolution
57. Autowiring Cons: • Black Magic • Performance (sometimes) @MPOram Pros: • No factories • No DIC configuration • Easy to use • Multi-stage dependency resolution
58. Autowiring Limitations: • Constructor injection only @MPOram
59. Autowiring Limitations: • Constructor injection only • Cannot auto inject scala values @MPOram
60. How it actually works @MPOram
61. Autowiring - How it works 1. Get list of constructor dependencies @MPOram
62. Autowiring - How it works 1. Get list of constructor dependencies 2. Get the type hint for each dependency @MPOram
63. Autowiring - How it works 1. Get list of constructor dependencies 2. Get the type hint for each dependency 3. Get an instance of each typehint, either from the DIC or by creating a new instance @MPOram
64. Autowiring - How it works 1. Get list of constructor dependencies 2. Get the type hint for each dependency 3. Get an instance of each typehint, either from the DIC or by creating a new instance 4. Instantiate desired class with its dependencies @MPOram
66. $reflection = new ReflectionClass('UserModel'); $args = $reflection->getConstructor()->getParameters(); ReflectionClass @MPOram
67. $reflection = new ReflectionClass('UserModel'); $args = $reflection->getConstructor()->getParameters(); foreach ($args as $arg) { $dependencyName = $arg->getClass()->getName(); } ReflectionClass @MPOram
68. $reflection = new ReflectionClass('UserModel'); $args = $reflection->getConstructor()->getParameters(); $dependencies = []; foreach ($args as $arg) { $dependencyName = $arg->getClass()->getName(); $dependencies[] = $container->get($dependencyName); } return new UserModel(...$dependencies); ReflectionClass @MPOram
70. https:/ /php-di.org/doc/autowiring.html @MPOram
71. Thank You Questions? Feedback please @MPOram