NEW: Allow specifying a factory to use for creating services.

A service factory can be used for creating instances where a non-trivial
construction process is required. This is done by adding a `factory`
key to the service definition.

control/injector/InjectionCreator.php

@@ -1,20 +1,16 @@
 <?php
 
+use SilverStripe\Framework\Injector\Factory;
+
 /**
  * A class for creating new objects by the injector.
  *
  * @package framework
  * @subpackage injector
  */
-class InjectionCreator {
+class InjectionCreator implements Factory {
 
-	/**
-	 * @param string $object
-	 *					A string representation of the class to create
-	 * @param array $params
-	 *					An array of parameters to be passed to the constructor
-	 */
-	public function create($class, $params = array()) {
+	public function create($class, array $params = array()) {
 		$reflector = new ReflectionClass($class);
 
 		if (count($params)) {
@@ -23,4 +19,5 @@ class InjectionCreator {
 		
 		return $reflector->newInstance();
 	}
+
 }

control/injector/Injector.php

@@ -1,9 +1,13 @@
 <?php
 
-require_once dirname(__FILE__) . '/InjectionCreator.php';
-require_once dirname(__FILE__) . '/SilverStripeInjectionCreator.php';
-require_once dirname(__FILE__) . '/ServiceConfigurationLocator.php';
-require_once dirname(__FILE__) . '/SilverStripeServiceConfigurationLocator.php';
+require_once FRAMEWORK_PATH . '/src/SilverStripe/Framework/Injector/Factory.php';
+
+require_once __DIR__ . '/InjectionCreator.php';
+require_once __DIR__ . '/SilverStripeInjectionCreator.php';
+require_once __DIR__ . '/ServiceConfigurationLocator.php';
+require_once __DIR__ . '/SilverStripeServiceConfigurationLocator.php';
+
+use SilverStripe\Framework\Injector\Factory;
 
 /**
  * A simple injection manager that manages creating objects and injecting
@@ -71,6 +75,7 @@ require_once dirname(__FILE__) . '/SilverStripeServiceConfigurationLocator.php';
  *			                                                // type
  *															// By default, singleton is assumed
  *
+ *			'factory' => 'FactoryService'					// A factory service to use to create instances.
  *			'construct'		=> array(						// properties to set at construction
  *				'scalar',									
  *				'%$BeanId',
@@ -163,14 +168,16 @@ class Injector {
 	private $autoScanProperties = false;
 
 	/**
-	 * The object used to create new class instances
+	 * The default factory used to create new instances.
 	 *
-	 * Use a custom class here to change the way classes are created to use
-	 * a custom creation method. By default the InjectionCreator class is used,
-	 * which simply creates a new class via 'new', however this could be overridden
-	 * to use, for example, SilverStripe's Object::create() method.
+	 * The {@link InjectionCreator} is used by default, which simply directly
+	 * creates objects. This can be changed to use a different default creation
+	 * method if desired.
 	 *
-	 * @var InjectionCreator
+	 * Each individual component can also specify a custom factory to use by
+	 * using the `factory` parameter.
+	 *
+	 * @var Factory
 	 */
 	protected $objectCreator;
 
@@ -216,6 +223,15 @@ class Injector {
 		return self::$instance;
 	}
 
+	/**
+	 * Sets the default global injector instance.
+	 *
+	 * @param Injector $instance
+	 */
+	public static function set_inst(Injector $instance) {
+		self::$instance = $instance;
+	}
+
 	/**
 	 * Indicate whether we auto scan injected objects for properties to set. 
 	 *
@@ -226,17 +242,16 @@ class Injector {
 	}
 	
 	/**
-	 * Sets the object to use for creating new objects
+	 * Sets the default factory to use for creating new objects.
 	 *
-	 * @param InjectionCreator $obj 
+	 * @param Factory $obj
 	 */
-	public function setObjectCreator($obj) {
+	public function setObjectCreator(Factory $obj) {
 		$this->objectCreator = $obj;
 	}
 	
 	/**
-	 * Accessor (for testing purposes)
-	 * @return InjectionCreator
+	 * @return Factory
 	 */
 	public function getObjectCreator() {
 		return $this->objectCreator;
@@ -486,7 +501,8 @@ class Injector {
 			$constructorParams = $spec['constructor'];
 		}
 
-		$object = $this->objectCreator->create($class, $constructorParams);
+		$factory = isset($spec['factory']) ? $this->get($spec['factory']) : $this->getObjectCreator();
+		$object = $factory->create($class, $constructorParams);
 
 		// figure out if we have a specific id set or not. In some cases, we might be instantiating objects
 		// that we don't manage directly; we don't want to store these in the service cache below

control/injector/SilverStripeInjectionCreator.php

@@ -1,22 +1,18 @@
 <?php
 
+use SilverStripe\Framework\Injector\Factory;
+
 /**
  * @package framework
  * @subpackage injector
  */
+class SilverStripeInjectionCreator implements Factory {
 
-class SilverStripeInjectionCreator {
-	/**
-	 *
-	 * @param string $object
-	 *					A string representation of the class to create
-	 * @param array $params
-	 *					An array of parameters to be passed to the constructor
-	 */
-	public function create($class, $params = array()) {
+	public function create($class, array $params = array()) {
 		$class = Object::getCustomClass($class);
 		$reflector = new ReflectionClass($class);
 
-		return $reflector->newInstanceArgs($params);
+		return $params ? $reflector->newInstanceArgs($params) : $reflector->newInstance();
 	}
+
 }

docs/en/reference/injector.md

@@ -78,7 +78,6 @@ In this case, on creation of the MyController object, the injector will
 automatically instantiate the PermissionService object and set it as
 the **permissions** property.
 
-
 ## Configuring objects managed by the dependency injector
 
 The above declarative style of dependency management would cover a large
@@ -90,6 +89,31 @@ Configuration can be specified for two areas of dependency management
 * Defining dependency overrides for individual classes
 * Injector managed 'services' 
 
+### Factories
+
+Some services require non-trivial construction which means they must be created by a factory class. To do this, create
+a factory class which implements the `[api:SilverStripe\Framework\Injector\Factory]` interface. You can then specify
+the `factory` key in the service definition, and the factory service will be used.
+
+An example using the `MyFactory` service to create instances of the `MyService` service is shown below:
+
+	:::yml
+	Injector:
+	  MyService:
+	    factory: MyFactory
+	  MyFactory:
+	    class: MyFactoryImplementation
+
+	:::php
+	class MyFactoryImplementation implements SilverStripe\Framework\Injector\Factory {
+		public function create($service, array $params = array()) {
+			return new MyServiceImplementation();
+		}
+	}
+
+	// Will use MyFactoryImplementation::create() to create the service instance.
+	$instance = Injector::inst()->get('MyService');
+
 ### Dependency overrides
 
 To override the **static $dependency;** declaration for a class, you could 

src/SilverStripe/Framework/Injector/Factory.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace SilverStripe\Framework\Injector;
+
+/**
+ * A factory which is used for creating service instances.
+ */
+interface Factory {
+
+	/**
+	 * Creates a new service instance.
+	 *
+	 * @param string $service The class name of the service.
+	 * @param array $params The constructor parameters.
+	 * @return object The created service instances.
+	 */
+	public function create($service, array $params = array());
+
+}

tests/injector/InjectorTest.php

@@ -541,6 +541,28 @@ class InjectorTest extends SapphireTest {
 		$this->assertEquals($item->property, 'othervalue');
 	}
 
+	/**
+	 * Tests creating a service with a custom factory.
+	 */
+	public function testCustomFactory() {
+		$injector = new Injector(array(
+			'service' => array('factory' => 'factory', 'constructor' => array(1, 2, 3))
+		));
+
+		$factory = $this->getMock('SilverStripe\\Framework\\Injector\\Factory');
+		$factory
+			->expects($this->once())
+			->method('create')
+			->with($this->equalTo('service'), $this->equalTo(array(1, 2, 3)))
+			->will($this->returnCallback(function($args) {
+				return new TestObject();
+			}));
+
+		$injector->registerService($factory, 'factory');
+
+		$this->assertInstanceOf('TestObject', $injector->get('service'));
+	}
+
 }
 
 class InjectorTestConfigLocator extends SilverStripeServiceConfigurationLocator implements TestOnly {
@@ -667,7 +689,7 @@ class SSObjectCreator extends InjectionCreator {
 		$this->injector = $injector;
 	}
 
-	public function create($class, $params = array()) {
+	public function create($class, array $params = array()) {
 		if (strpos($class, '(') === false) {
 			return parent::create($class, $params);
 		} else {