New features for Singleton object

src/eTools/Utils/Singleton.php

@@ -13,14 +13,53 @@ abstract class Singleton {
 
     protected static $instances = array();
 
+	private static $override_instances = array();
+
+	/**
+	 * Returns a singleton object of a given class. Extend this class, then call \YourClass::getInstance() from anywhere
+	 * in the application.
+	 *
+	 * If an override class is registered, that will be returned instead. Thi
+	 *
+	 * @return \stdClass A singleton of the requested class
+	 */
     public static function getInstance() {
         $class = get_called_class();
+		$args = func_get_args();
+
+		// Check if an override is set, and replace the class name to load if it is
+		if (isset(self::$override_instances[$class])) {
+			$class = self::$override_instances[$class];
+		}
+
+		// Create a singleton instance of the class if it doesn't already exist
         if (!isset(self::$instances[$class])) {
-            self::$instances[$class] = new $class();
+			if(is_array($args) && sizeof($args) > 0) {
+				$reflectionClass = new \ReflectionClass($class);
+				self::$instances[$class] = $reflectionClass->newInstanceArgs($args);
+			} else {
+				self::$instances[$class] = new $class();
+			}
         }
+
         return self::$instances[$class];
     }
 
+	/**
+	 * Configures an override class, that can later be returned by self::getInstance().
+	 *
+	 * @param string $oldClass The class name to replace
+	 * @param string $newClass The class to replace this with
+	 * @return void
+	 */
+	public static function set_override_instance($oldClass, $newClass) {
+		self::$override_instances[$oldClass] = $newClass;
+	}
+
+	public static function clear_instances() {
+		self::$instances = array();
+	}
+
     protected function __construct() {
 
     }

tests/eTools/Utils/SingletonTest.php

@@ -0,0 +1,91 @@
+<?php
+namespace eTools\Tests\Utils;
+
+use eTools\Utils\Singleton;
+
+class SingletonTest extends \PHPUnit_Framework_TestCase {
+	public function setUp() {
+		Singleton::clear_instances();
+	}
+
+	/**
+	 * This tests ensures that the Singleton::getInstance() method always returns the same object every time you call it
+	 */
+	public function testGetInstance() {
+		/** @var SingletonSubclass $obj */
+		$obj = SingletonSubclass::getInstance();
+		$this->assertEquals(false, $obj->getCheck());
+		$obj->toggleCheck();
+
+		/** @var SingletonSubclass $obj2 */
+		$obj2 = SingletonSubclass::getInstance();
+		$this->assertEquals(true, $obj2->getCheck());
+
+		$obj2->toggleCheck();
+		$this->assertEquals(false, $obj->getCheck());
+	}
+
+	public function testGetInstanceSetsConstructorArgs() {
+		/** @var SingletonSubclass $obj */
+		$obj = SingletonSubclass::getInstance('arg1', 'arg2');
+		$this->assertEquals('arg1', $obj->getConstructorArg1());
+		$this->assertEquals('arg2', $obj->getConstructorArg2());
+	}
+
+	/**
+	 * This test ensures that the Singleton::set_override_instance() method overrides classes correctly
+	 */
+	public function testOverrideInstances() {
+		// Before setting an override, we should get the normal class
+		$singletonSubclass = SingletonSubclass::getInstance();
+		$this->assertInstanceOf('eTools\Tests\Utils\SingletonSubclass', $singletonSubclass);
+
+		// Set the override and try again, we should now get the overridden method
+		Singleton::set_override_instance(
+			'eTools\Tests\Utils\SingletonSubclass',
+			'eTools\Tests\Utils\SingletonOverrideSubclass'
+		);
+
+		// Ensure it hasn't changed the existing instance somehow
+		$this->assertInstanceOf('eTools\Tests\Utils\SingletonSubclass', $singletonSubclass);
+		$this->assertInstanceOf('eTools\Tests\Utils\SingletonOverrideSubclass', SingletonSubclass::getInstance());
+
+		// Ensure override works every time once it's set
+		$this->assertInstanceOf('eTools\Tests\Utils\SingletonOverrideSubclass', SingletonSubclass::getInstance());
+	}
+}
+
+/**
+ * Class SingletonSubclass
+ * @package eTools\Tests\Utils
+ *
+ * This is a sample class - it should be used only for testing
+ */
+class SingletonSubclass extends Singleton {
+	private $check = false;
+	private $constructorArg1 = null;
+	private $constructorArg2 = null;
+
+	public function __construct($arg1 = null, $arg2 = null) {
+		$this->constructorArg1 = $arg1;
+		$this->constructorArg2 = $arg2;
+	}
+
+	public function toggleCheck() {
+		$this->check = !$this->check;
+	}
+
+	public function getCheck() {
+		return $this->check;
+	}
+
+	public function getConstructorArg1() {
+		return $this->constructorArg1;
+	}
+
+	public function getConstructorArg2() {
+		return $this->constructorArg2;
+	}
+}
+
+class SingletonOverrideSubclass extends Singleton {}