Dependency Injector
A simple and lightweight dependency injector. You will need nothing more to tests your old legacy code.
Did you ever wondered how complicated it could be to write a dependency injector that works? In fact it is very easy and you don't need a tons of classes laying around and learn a dozens of new fancy words.
It is just a storage of functions and values for a specific key. Store your function to create an instance and it get executed the first time you need this instance.
Sounds to easy? What about dependencies? Check the examples. It is nothing more needed than this.
What is a dependency
Something that your script needs to work correct. For example an instance of Calculator or Config. Or even
a class itself.
Examples
The Config
<?php
use DependencyInjector\DI;
class Config {
private static $_instance;
public $database = [
'host' => 'localhost',
'user' => 'john',
'password' => 'does.secret',
'database' => 'john_doe'
];
public $redis = ['host' => 'localhost'];
private function __construct() {
// maybe some logic to change the config or initialize variables
}
public static function getInstance() {
if (!self::$_instance) {
self::$_instance = new Config();
}
return self::$_instance;
}
}
DI::set('config', function() { return Config::getInstance(); });
function someStaticFunction() {
// before
if (empty(Config::getInstance()->database['host'])) {
throw new Exception('No database host configured');
}
// now
if (empty(DI::config()->database['host'])) {
throw new Exception('No database host configured');
}
// or if you prefer
if (empty(DI::get('config')->database['host'])) {
throw new Exception('No database host configured');
}
}The database connection
<?php
use DependencyInjector\DI;
DI::set('database', function() {
$dbConfig = DI::config()->database;
$mysql = new mysqli($dbConfig['host'], $dbConfig['user'], $dbConfig['password'], $dbConfig['database']);
if (!empty($mysql->connect_error)) {
throw new Exception('could not connect to database (' . $mysql->connect_error . ')');
}
return $mysql;
});
function someStaticFunction() {
// before it maybe looked like this
$mysql = MyApp::getDatabaseConnection();
// now
$mysql = DI::database();
$mysql->query('SELECT * FROM table');
}The problem before: you can not mock the static function MyApp::getDatabaseConnection(). You also can not mock the
static function DI::database() or DI::get('database'). But you can set the dependency to return a mock object:
<?php
use DependencyInjector\DI;
class ApplicationTest extends PHPUnit_Framework_TestCase {
public function testSomeStaticFunction() {
$mock = $this->getMock(mysqli::class);
$mock->expects($this->once())->method('query')
->with('SELECT * FROM table');
DI::set('database', function() use($mock) { return $mock; });
someStaticFunction();
}
}