Dependency Injection

Reinventing how you manage PHP classes

Transcript

1. Dependency Injection Reinventing how you manage PHP classes
2. DI? What is DI?
3. Dependency Injection means giving an object its instance variables. Really. That's it. - James Shore The Really Short Version
4. Why This Kolaveri DI?
5. Why This Kolaveri DI? CHANGE
6. Why DI? • Maintainable • Extendible • Flexible • Configurable • Testable • Reusable • Interoperable
7. A Real Life Example
8. “Dependency Injection” is a 25-dollar term for a 5-cent concept. Don’t Panic!
9. A PHP Example
10. class MySqlDB { private $_link; public function __construct($host, $username, $password, $database) { $this->_link = mysql_connect($host, $username, $password); mysql_select_db($database); } public function insert($data, $table) { array_map('mysql_real_escape_string', $data); $query = 'INSERT INTO `' . $table . '` (`' . implode('`,`', array_keys($data)) . '`)' . 'VALUES ("' . implode('","', $data) . '" )'; return mysql_query($query, $this->_link); } // ... }
11. define('MYSQL_HOST', 'localhost'); define('MYSQL_USER', 'root'); define('MYSQL_PASS', ''); define('MYSQL_DB', 'test'); class User { private $_db; private $_info = array(); public function __construct() { $this->_db = new MySqlDB(MYSQL_HOST, MYSQL_USER, MYSQL_PASS, MYSQL_DB); } public function register($name, $email, $age, $sex) { $this->_info = compact('name', 'email', 'age', 'sex'); $this->_db->insert($this->_info, 'users'); } // ... } $user = new User(); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female');
12. // You can hardcode it public function __construct() { $this->_db = new MySqlDB('localhost', 'root', '', 'test'); } // You can configure it with an array public function __construct($config) { $this->_db = new MySqlDB($config['host'], $config['user'], $config['pass'], $config['db']); } // And, What we saw earlier public function __construct() { $this->_db = new MySqlDB(MYSQL_HOST, MYSQL_USER, MYSQL_PASS, MYSQL_DB); } Options
13. What if I want to use a different database like MongoDB or SQLite
14. Hey wait, I can improve it!
15. class User { protected $_db; protected $_info = array(); public function __construct() { $registry = RegistrySingleton::getInstance(); $this->_db = $registry->database; } public function register($name, $email, $age, $sex) { $this->_info = compact('name', 'email', 'age', 'sex'); $this->_db->insert($this->info, 'users'); } // ... } $user = new User(); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female');
16. Smart Huh???
17. So, now User depends on Registry
18. Let’s do it with DI
19. class User { protected $_db; protected $_info = array(); public function __construct($database) { $this->_db = $database; } public function register($name, $email, $age, $sex) { $this->_info = compact('name', 'email', 'age', 'sex'); $this->_db->insert($this->_info, 'users'); } // ... } $mysql = new MySqlDB('localhost', 'root', '', 'test'); $user = new User($mysql); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female');
20. But there are still rooms for improvement
21. Interface
22. Ever heard of Type Hinting
23. public function test(OtherClass $otherClass) { } public function testInterface(Interface $interface) { } public function testArray(array $inputArray) { } Type Hinting Since PHP 5.1
24. interface Database { public function insert(array $data, $table); } class User { protected $_db; protected $_info = array(); public function __construct(Database $database) { $this->_db = $database; } public function register($name, $email, $age, $sex) { $this->_info = compact('name', 'email', 'age', 'sex'); $this->_db->insert($this->_info, 'users'); } // ... } $mysql = new MySqlDB('localhost', 'root', '', 'test'); $user = new User($mysql); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female');
25. class MySqlDB implements Database { protected $_link; public function __construct($host, $username, $password, $database) { $this->_link = mysql_connect($host, $username, $password); mysql_select_db($database); } public function insert(array $data, $table) { array_map('mysql_real_escape_string', $data); $query = 'INSERT INTO `' . $table . '` (`' . implode('`,`', array_keys($data)) . '`)' . 'VALUES ("' . implode('","', $data) . '" )'; return mysql_query($query, $this->_link); } // ... } MySQL
26. class MongoDB implements Database { // ... public function insert(array $data, $table) { // Save the passed array using MongoDB } // ... } $mongoDb = new MongoDB('localhost', 'root', '', 'test'); $user = new User($mongoDb); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female'); MongoDB
27. class SQLiteDB implements Database { // ... public function insert(array $data, $table) { // Save the passed array using SQLite } // ... } $sqlite = new SQLiteDB('app.db', 'test'); $user = new User($sqlite); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female'); SQLite
28. class TestDB implements Database { protected $_data = array(); public function insert(array $data, $table) { $this->_data[$table] = $data; } public function get($table) { return $this->_data[$table]; } } $fakeDb = new TestDB(); $user = new User($fakeDb); $user->register('Tasneem', 'tasmee@fb.me', 18, 'female'); print_r($fakeDb->get('users')); TestDB
29. DI Container
30. class Container { protected $s=array(); function __set($k, $c) { $this->s[$k]=$c; } function __get($k) { return $this->s[$k]($this); } } Twittee A DI Container in a Tweet using the power of PHP 5.3
31. $c = new Container(); $c->mysql = function ($c) { return new MySqlDB('localhost', 'root', '', 'test'); } $c->user = function ($c) { $db = $c->mysql; return new User($db); } // When you need a user $user = $c->user; // Instead of $user = new User(); Container
32. http://components.symfony-project.org/dependency-injection/ http://pimple.sensiolabs.org/ http://twittee.org/ More...
33. Question?
34. @rifat rifat@facebook.com http://VistaArc.com/ http://OmicronLab.com/ Thank You