Merge pull request #2788 from yiisoft/feature-container

docs/guide/basics.md

@@ -55,7 +55,7 @@ $object = Yii::createObject([
     'class' => 'MyClass',
     'property1' => 'abc',
     'property2' => 'cde',
-], $param1, $param2);
+], [$param1, $param2]);
 ```
 
 

docs/guide/configuration.md

@@ -93,26 +93,24 @@ In the above code, four components are configured: `cache`, `user`, `errorHandle
 The configuration array has one special key named `class` that identifies the component's base class. The rest of the keys and values are used
 to configure component properties in the same way as top-level keys are used to configure the application's properties.
 
-Each application has a predefined set of components. To configure one of these, the `class` key can be omitted to use the default Yii class for that component. You can check the `registerCoreComponents()` method of the application you are using
+Each application has a predefined set of components. To configure one of these, the `class` key can be omitted to use the default Yii class for that component. You can check the `coreComponents()` method of the application you are using
 to get a list of component IDs and corresponding classes.
 
 Note that Yii is smart enough to only configure the component when it's actually being used: for example, if you configure the `cache` component in your configuration file but never use the `cache` component in your code, no instance of that component will be created and no time is wasted configuring it.
 
-Setting component defaults classwide
+Setting component defaults class-wide
 ------------------------------------
 
-For each component you can specifiy classwide defaults. For example, if you want to change the class used for all `LinkPager`
+For each component you can specify class-wide defaults. For example, if you want to change the class used for all `LinkPager`
 widgets without specifying the class for every widget usage, you can do the following:
 
 ```php
-\Yii::$objectConfig = [
-	'yii\widgets\LinkPager' => [
-		'options' => [
-			'class' => 'pagination',
-		],
-	],
-];
+\Yii::$container->set('yii\widgets\LinkPager', [
+    'options' => [
+        'class' => 'pagination',
+    ],
+]);
 ```
 
 The code above should be executed once before `LinkPager` widget is used. It can be done in `index.php`, the application
-configuration file, or anywhere else.
+configuration file, or anywhere else.
\ No newline at end of file

docs/guide/upgrade-from-v1.md

@@ -71,7 +71,7 @@ $object = Yii::createObject([
     'class' => 'MyClass',
     'property1' => 'abc',
     'property2' => 'cde',
-], $param1, $param2);
+], [$param1, $param2]);
 ```
 
 More on configuration can be found in the [Basic concepts section](basics.md).

extensions/authclient/AuthAction.php

@@ -164,7 +164,7 @@ class AuthAction extends Action
         if (!empty($_GET[$this->clientIdGetParamName])) {
             $clientId = $_GET[$this->clientIdGetParamName];
             /** @var \yii\authclient\Collection $collection */
-            $collection = Yii::$app->getComponent($this->clientCollection);
+            $collection = Yii::$app->get($this->clientCollection);
             if (!$collection->hasClient($clientId)) {
                 throw new NotFoundHttpException("Unknown auth client '{$clientId}'");
             }

extensions/authclient/widgets/Choice.php

@@ -143,7 +143,7 @@ class Choice extends Widget
     protected function defaultClients()
     {
         /** @var $collection \yii\authclient\Collection */
-        $collection = Yii::$app->getComponent($this->clientCollection);
+        $collection = Yii::$app->get($this->clientCollection);
 
         return $collection->getClients();
     }

extensions/debug/panels/RequestPanel.php

@@ -86,7 +86,7 @@ class RequestPanel extends Panel
             $action = null;
         }
         /** @var \yii\web\Session $session */
-        $session = Yii::$app->getComponent('session', false);
+        $session = Yii::$app->has('session', true) ? Yii::$app->get('session') : null;
 
         return [
             'flashes' => $session ? $session->getAllFlashes() : [],

extensions/elasticsearch/ActiveRecord.php

@@ -59,7 +59,7 @@ class ActiveRecord extends BaseActiveRecord
      */
     public static function getDb()
     {
-        return \Yii::$app->getComponent('elasticsearch');
+        return \Yii::$app->get('elasticsearch');
     }
 
     /**

extensions/elasticsearch/DebugAction.php

@@ -55,7 +55,7 @@ class DebugAction extends Action
         $options = ['pretty' => true];
 
         /** @var Connection $db */
-        $db = \Yii::$app->getComponent($this->db);
+        $db = \Yii::$app->get($this->db);
         $time = microtime(true);
         switch ($method) {
             case 'GET': $result = $db->get($url, $options, $body, true); break;

extensions/elasticsearch/Query.php

@@ -115,7 +115,7 @@ class Query extends Component implements QueryInterface
     public function createCommand($db = null)
     {
         if ($db === null) {
-            $db = Yii::$app->getComponent('elasticsearch');
+            $db = Yii::$app->get('elasticsearch');
         }
 
         $commandConfig = $db->getQueryBuilder()->build($this);

extensions/gii/generators/model/Generator.php

@@ -437,9 +437,9 @@ class Generator extends \yii\gii\Generator
      */
     public function validateDb()
     {
-        if (Yii::$app->hasComponent($this->db) === false) {
+        if (!Yii::$app->has($this->db)) {
             $this->addError('db', 'There is no application component named "db".');
-        } elseif (!Yii::$app->getComponent($this->db) instanceof Connection) {
+        } elseif (!Yii::$app->get($this->db) instanceof Connection) {
             $this->addError('db', 'The "db" application component must be a DB connection instance.');
         }
     }

extensions/mongodb/ActiveRecord.php

@@ -29,7 +29,7 @@ abstract class ActiveRecord extends BaseActiveRecord
      */
     public static function getDb()
     {
-        return \Yii::$app->getComponent('mongodb');
+        return \Yii::$app->get('mongodb');
     }
 
     /**

extensions/mongodb/Cache.php

@@ -9,6 +9,7 @@ namespace yii\mongodb;
 
 use Yii;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 
 /**
  * Cache implements a cache application component by storing cached data in a MongoDB.
@@ -61,12 +62,7 @@ class Cache extends \yii\caching\Cache
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException($this->className() . "::db must be either a MongoDB connection instance or the application component ID of a MongoDB connection.");
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 
     /**

extensions/mongodb/Query.php

@@ -62,7 +62,7 @@ class Query extends Component implements QueryInterface
     public function getCollection($db = null)
     {
         if ($db === null) {
-            $db = Yii::$app->getComponent('mongodb');
+            $db = Yii::$app->get('mongodb');
         }
 
         return $db->getCollection($this->from);

extensions/mongodb/Session.php

@@ -9,6 +9,7 @@ namespace yii\mongodb;
 
 use Yii;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 
 /**
  * Session extends [[\yii\web\Session]] by using MongoDB as session data storage.
@@ -55,13 +56,8 @@ class Session extends \yii\web\Session
      */
     public function init()
     {
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException($this->className() . "::db must be either a MongoDB connection instance or the application component ID of a MongoDB connection.");
-        }
         parent::init();
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 
     /**

extensions/mongodb/file/Query.php

@@ -31,7 +31,7 @@ class Query extends \yii\mongodb\Query
     public function getCollection($db = null)
     {
         if ($db === null) {
-            $db = Yii::$app->getComponent('mongodb');
+            $db = Yii::$app->get('mongodb');
         }
 
         return $db->getFileCollection($this->from);

extensions/redis/ActiveRecord.php

@@ -45,7 +45,7 @@ class ActiveRecord extends BaseActiveRecord
      */
     public static function getDb()
     {
-        return \Yii::$app->getComponent('redis');
+        return \Yii::$app->get('redis');
     }
 
     /**

extensions/redis/Cache.php

@@ -76,7 +76,7 @@ class Cache extends \yii\caching\Cache
     {
         parent::init();
         if (is_string($this->redis)) {
-            $this->redis = Yii::$app->getComponent($this->redis);
+            $this->redis = Yii::$app->get($this->redis);
         } elseif (is_array($this->redis)) {
             if (!isset($this->redis['class'])) {
                 $this->redis['class'] = Connection::className();

extensions/redis/Session.php

@@ -80,7 +80,7 @@ class Session extends \yii\web\Session
     public function init()
     {
         if (is_string($this->redis)) {
-            $this->redis = Yii::$app->getComponent($this->redis);
+            $this->redis = Yii::$app->get($this->redis);
         } elseif (is_array($this->redis)) {
             if (!isset($this->redis['class'])) {
                 $this->redis['class'] = Connection::className();

extensions/sphinx/ActiveRecord.php

@@ -62,7 +62,7 @@ abstract class ActiveRecord extends BaseActiveRecord
      */
     public static function getDb()
     {
-        return \Yii::$app->getComponent('sphinx');
+        return \Yii::$app->get('sphinx');
     }
 
     /**

extensions/sphinx/Query.php

@@ -155,7 +155,7 @@ class Query extends Component implements QueryInterface
      */
     protected function defaultConnection()
     {
-        return Yii::$app->getComponent('sphinx');
+        return Yii::$app->get('sphinx');
     }
 
     /**

extensions/sphinx/Schema.php

@@ -132,7 +132,7 @@ class Schema extends Object
 
         if ($db->enableSchemaCache && !in_array($name, $db->schemaCacheExclude, true)) {
             /** @var $cache Cache */
-            $cache = is_string($db->schemaCache) ? Yii::$app->getComponent($db->schemaCache) : $db->schemaCache;
+            $cache = is_string($db->schemaCache) ? Yii::$app->get($db->schemaCache, false) : $db->schemaCache;
             if ($cache instanceof Cache) {
                 $key = $this->getCacheKey($name);
                 if ($refresh || ($index = $cache->get($key)) === false) {
@@ -296,7 +296,7 @@ class Schema extends Object
     public function refresh()
     {
         /** @var $cache Cache */
-        $cache = is_string($this->db->schemaCache) ? Yii::$app->getComponent($this->db->schemaCache) : $this->db->schemaCache;
+        $cache = is_string($this->db->schemaCache) ? Yii::$app->get($this->db->schemaCache, false) : $this->db->schemaCache;
         if ($this->db->enableSchemaCache && $cache instanceof Cache) {
             GroupDependency::invalidate($cache, $this->getCacheGroup());
         }

extensions/swiftmailer/Mailer.php

@@ -200,10 +200,9 @@ class Mailer extends BaseMailer
                 }
             }
             unset($config['constructArgs']);
-            array_unshift($args, $className);
-            $object = call_user_func_array(['Yii', 'createObject'], $args);
+            $object = Yii::createObject($className, $args);
         } else {
-            $object = new $className;
+            $object = Yii::createObject($className);
         }
         if (!empty($config)) {
             foreach ($config as $name => $value) {

framework/BaseYii.php

@@ -10,6 +10,7 @@ use yii\base\InvalidConfigException;
 use yii\base\InvalidParamException;
 use yii\base\UnknownClassException;
 use yii\log\Logger;
+use yii\di\Container;
 
 /**
  * Gets the application start timestamp.
@@ -76,26 +77,13 @@ class BaseYii
      */
     public static $aliases = ['@yii' => __DIR__];
     /**
-     * @var array initial property values that will be applied to objects newly created via [[createObject]].
-     * The array keys are class names without leading backslashes "\", and the array values are the corresponding
-     * name-value pairs for initializing the created class instances. For example,
-     *
-     * ~~~
-     * [
-     *     'Bar' => [
-     *         'prop1' => 'value1',
-     *         'prop2' => 'value2',
-     *     ],
-     *     'mycompany\foo\Car' => [
-     *         'prop1' => 'value1',
-     *         'prop2' => 'value2',
-     *     ],
-     * ]
-     * ~~~
-     *
+     * @var Container the dependency injection (DI) container used by [[createObject()]].
+     * You may use [[Container::set()]] to set up the needed dependencies of classes and
+     * their initial property values.
      * @see createObject()
+     * @see Container
      */
-    public static $objectConfig = [];
+    public static $container;
 
 
     /**
@@ -304,74 +292,59 @@ class BaseYii
     /**
      * Creates a new object using the given configuration.
      *
-     * The configuration can be either a string or an array.
-     * If a string, it is treated as the *object class*; if an array,
-     * it must contain a `class` element specifying the *object class*, and
-     * the rest of the name-value pairs in the array will be used to initialize
-     * the corresponding object properties.
+     * You may view this method as an enhanced version of the `new` operator.
+     * The method supports creating an object based on a class name, a configuration array or
+     * an anonymous function.
      *
      * Below are some usage examples:
      *
-     * ~~~
-     * $object = \Yii::createObject('app\components\GoogleMap');
-     * $object = \Yii::createObject([
-     *     'class' => 'app\components\GoogleMap',
-     *     'apiKey' => 'xyz',
+     * ```php
+     * // create an object using a class name
+     * $object = Yii::createObject('yii\db\Connection');
+     *
+     * // create an object using a configuration array
+     * $object = Yii::createObject([
+     *     'class' => 'yii\db\Connection',
+     *     'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
+     *     'username' => 'root',
+     *     'password' => '',
+     *     'charset' => 'utf8',
      * ]);
-     * ~~~
      *
-     * This method can be used to create any object as long as the object's constructor is
-     * defined like the following:
+     * // create an object with two constructor parameters
+     * $object = \Yii::createObject('MyClass', [$param1, $param2]);
+     * ```
      *
-     * ~~~
-     * public function __construct(..., $config = []) {
-     * }
-     * ~~~
+     * Using [[\yii\di\Container|dependency injection container]], this method can also identify
+     * dependent objects, instantiate them and inject them into the newly created object.
+     *
+     * @param string|array|callable $type the object type. This can be specified in one of the following forms:
      *
-     * The method will pass the given configuration as the last parameter of the constructor,
-     * and any additional parameters to this method will be passed as the rest of the constructor parameters.
+     * - a string: representing the class name of the object to be created
+     * - a configuration array: the array must contain a `class` element which is treated as the object class,
+     *   and the rest of the name-value pairs will be used to initialize the corresponding object properties
+     * - a PHP callable: either an anonymous function or an array representing a class method (`[$class or $object, $method]`).
+     *   The callable should return a new instance of the object being created.
      *
-     * @param  string|array           $config the configuration. It can be either a string representing the class name
-     *                                        or an array representing the object configuration.
-     * @return mixed                  the created object
+     * @param array $params the constructor parameters
+     * @return object the created object
      * @throws InvalidConfigException if the configuration is invalid.
+     * @see \yii\di\Container
      */
-    public static function createObject($config)
+    public static function createObject($type, array $params = [])
     {
-        static $reflections = [];
-
-        if (is_string($config)) {
-            $class = $config;
-            $config = [];
-        } elseif (isset($config['class'])) {
-            $class = $config['class'];
-            unset($config['class']);
-        } else {
+        if (is_string($type)) {
+            return static::$container->get($type, $params);
+        } elseif (is_array($type) && isset($type['class'])) {
+            $class = $type['class'];
+            unset($type['class']);
+            return static::$container->get($class, $params, $type);
+        } elseif (is_callable($type, true)) {
+            return call_user_func($type, $params);
+        } elseif (is_array($type)) {
             throw new InvalidConfigException('Object configuration must be an array containing a "class" element.');
-        }
-
-        $class = ltrim($class, '\\');
-
-        if (isset(static::$objectConfig[$class])) {
-            $config = array_merge(static::$objectConfig[$class], $config);
-        }
-
-        if (func_num_args() > 1) {
-            /** @var \ReflectionClass $reflection */
-            if (isset($reflections[$class])) {
-                $reflection = $reflections[$class];
-            } else {
-                $reflection = $reflections[$class] = new \ReflectionClass($class);
-            }
-            $args = func_get_args();
-            array_shift($args); // remove $config
-            if (!empty($config)) {
-                $args[] = $config;
-            }
-
-            return $reflection->newInstanceArgs($args);
         } else {
-            return empty($config) ? new $class : new $class($config);
+            throw new InvalidConfigException("Unsupported configuration type: " . gettype($type));
         }
     }
 

framework/CHANGELOG.md

@@ -248,7 +248,11 @@ Yii Framework 2 Change Log
 - Chg: Added `View::viewFile` and removed `ViewEvent::viewFile` (qiangxue)
 - Chg: Changed `Controller::afterAction()`, `Module::afterAction()` and `ActionFilter::afterAction()` to pass `$result` by value instead of reference (qiangxue)
 - Chg: `yii\base\Extension::init()` is renamed to `bootstrap()` (qiangxue)
+- Chg: `getComponent()` and `setComponent()` in `Application` and `Module` are renamed to `get()` and `set()` respectively. (qiangxue)
+- Chg: The signature of `Yii::createObject()` is changed. Constructor parameters must be passed as the second parameter. (qiangxue)
+- Chg: `Yii::$objectConfig` is removed. You should use `Yii::$container->set()` to configure default settings of classes. (qiangxue)
 - New #66: [Auth client library](https://github.com/yiisoft/yii2-authclient) OpenId, OAuth1, OAuth2 clients (klimov-paul)
+- New #503: Added `yii\di\Container` and `yii\di\ServiceLocator` (qiangxue)
 - New #706: Added `yii\widgets\Pjax` and enhanced `GridView` to work with `Pjax` to support AJAX-update (qiangxue)
 - New #1393: [Codeception testing framework integration](https://github.com/yiisoft/yii2-codeception) (Ragazzo)
 - New #1438: [MongoDB integration](https://github.com/yiisoft/yii2-mongodb) ActiveRecord and Query (klimov-paul)

framework/Yii.php

@@ -24,3 +24,4 @@ class Yii extends \yii\BaseYii
 
 spl_autoload_register(['Yii', 'autoload'], true, true);
 Yii::$classMap = include(__DIR__ . '/classes.php');
+Yii::$container = new yii\di\Container;

framework/base/Application.php

@@ -160,7 +160,6 @@ abstract class Application extends Module
 
         $this->preInit($config);
         $this->registerErrorHandlers();
-        $this->registerCoreComponents();
 
         Component::__construct($config);
     }
@@ -206,6 +205,15 @@ abstract class Application extends Module
         } elseif (!ini_get('date.timezone')) {
             $this->setTimeZone('UTC');
         }
+
+        // merge core components with custom components
+        foreach ($this->coreComponents() as $id => $component) {
+            if (!isset($config['components'][$id])) {
+                $config['components'][$id] = $component;
+            } elseif (is_array($config['components'][$id]) && !isset($config['components'][$id]['class'])) {
+                $config['components'][$id]['class'] = $component['class'];
+            }
+        }
     }
 
     /**
@@ -248,7 +256,7 @@ abstract class Application extends Module
      */
     public function preloadComponents()
     {
-        $this->getComponent('log');
+        $this->get('log');
         parent::preloadComponents();
     }
 
@@ -400,7 +408,7 @@ abstract class Application extends Module
      */
     public function getDb()
     {
-        return $this->getComponent('db');
+        return $this->get('db');
     }
 
     /**
@@ -409,7 +417,7 @@ abstract class Application extends Module
      */
     public function getLog()
     {
-        return $this->getComponent('log');
+        return $this->get('log');
     }
 
     /**
@@ -418,7 +426,7 @@ abstract class Application extends Module
      */
     public function getErrorHandler()
     {
-        return $this->getComponent('errorHandler');
+        return $this->get('errorHandler');
     }
 
     /**
@@ -427,7 +435,7 @@ abstract class Application extends Module
      */
     public function getCache()
     {
-        return $this->getComponent('cache');
+        return $this->get('cache');
     }
 
     /**
@@ -436,7 +444,7 @@ abstract class Application extends Module
      */
     public function getFormatter()
     {
-        return $this->getComponent('formatter');
+        return $this->get('formatter');
     }
 
     /**
@@ -445,7 +453,7 @@ abstract class Application extends Module
      */
     public function getRequest()
     {
-        return $this->getComponent('request');
+        return $this->get('request');
     }
 
     /**
@@ -454,7 +462,7 @@ abstract class Application extends Module
      */
     public function getView()
     {
-        return $this->getComponent('view');
+        return $this->get('view');
     }
 
     /**
@@ -463,7 +471,7 @@ abstract class Application extends Module
      */
     public function getUrlManager()
     {
-        return $this->getComponent('urlManager');
+        return $this->get('urlManager');
     }
 
     /**
@@ -472,7 +480,7 @@ abstract class Application extends Module
      */
     public function getI18n()
     {
-        return $this->getComponent('i18n');
+        return $this->get('i18n');
     }
 
     /**
@@ -481,7 +489,7 @@ abstract class Application extends Module
      */
     public function getMail()
     {
-        return $this->getComponent('mail');
+        return $this->get('mail');
     }
 
     /**
@@ -490,16 +498,16 @@ abstract class Application extends Module
      */
     public function getAuthManager()
     {
-        return $this->getComponent('authManager');
+        return $this->get('authManager');
     }
 
     /**
-     * Registers the core application components.
-     * @see setComponents
+     * Returns the core application components.
+     * @see set
      */
-    public function registerCoreComponents()
+    public function coreComponents()
     {
-        $this->setComponents([
+        return [
             'log' => ['class' => 'yii\log\Logger'],
             'errorHandler' => ['class' => 'yii\base\ErrorHandler'],
             'formatter' => ['class' => 'yii\base\Formatter'],
@@ -507,7 +515,7 @@ abstract class Application extends Module
             'mail' => ['class' => 'yii\swiftmailer\Mailer'],
             'urlManager' => ['class' => 'yii\web\UrlManager'],
             'view' => ['class' => 'yii\web\View'],
-        ]);
+        ];
     }
 
     /**

framework/base/Controller.php

@@ -192,7 +192,7 @@ class Controller extends Component implements ViewContextInterface
 
         $actionMap = $this->actions();
         if (isset($actionMap[$id])) {
-            return Yii::createObject($actionMap[$id], $id, $this);
+            return Yii::createObject($actionMap[$id], [$id, $this]);
         } elseif (preg_match('/^[a-z0-9\\-_]+$/', $id) && strpos($id, '--') === false && trim($id, '-') === $id) {
             $methodName = 'action' . str_replace(' ', '', ucwords(implode(' ', explode('-', $id))));
             if (method_exists($this, $methodName)) {

framework/base/Module.php

@@ -8,6 +8,7 @@
 namespace yii\base;
 
 use Yii;
+use yii\di\ServiceLocator;
 
 /**
  * Module is the base class for module and application classes.
@@ -35,7 +36,7 @@ use Yii;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class Module extends Component
+class Module extends ServiceLocator
 {
     /**
      * @var array custom module parameters (name => value).
@@ -110,10 +111,7 @@ class Module extends Component
      * @var array child modules of this module
      */
     private $_modules = [];
-    /**
-     * @var array components registered under this module
-     */
-    private $_components = [];
+
 
     /**
      * Constructor.
@@ -129,38 +127,6 @@ class Module extends Component
     }
 
     /**
-     * Getter magic method.
-     * This method is overridden to support accessing components
-     * like reading module properties.
-     * @param  string $name component or property name
-     * @return mixed  the named property value
-     */
-    public function __get($name)
-    {
-        if ($this->hasComponent($name)) {
-            return $this->getComponent($name);
-        } else {
-            return parent::__get($name);
-        }
-    }
-
-    /**
-     * Checks if a property value is null.
-     * This method overrides the parent implementation by checking
-     * if the named component is loaded.
-     * @param  string  $name the property name or the event name
-     * @return boolean whether the property value is null
-     */
-    public function __isset($name)
-    {
-        if ($this->hasComponent($name)) {
-            return $this->getComponent($name) !== null;
-        } else {
-            return parent::__isset($name);
-        }
-    }
-
-    /**
      * Initializes the module.
      * This method is called after the module is created and initialized with property values
      * given in configuration. The default implementation will call [[preloadComponents()]] to
@@ -350,7 +316,7 @@ class Module extends Component
                     $this->_modules[$id]['class'] = 'yii\base\Module';
                 }
 
-                return $this->_modules[$id] = Yii::createObject($this->_modules[$id], $id, $this);
+                return $this->_modules[$id] = Yii::createObject($this->_modules[$id], [$id, $this]);
             }
         }
 
@@ -432,126 +398,14 @@ class Module extends Component
     }
 
     /**
-     * Checks whether the named component exists.
-     * @param  string  $id component ID
-     * @return boolean whether the named component exists. Both loaded and unloaded components
-     *                    are considered.
-     */
-    public function hasComponent($id)
-    {
-        return isset($this->_components[$id]);
-    }
-
-    /**
-     * Retrieves the named component.
-     * @param  string         $id   component ID (case-sensitive)
-     * @param  boolean        $load whether to load the component if it is not yet loaded.
-     * @return Component|null the component instance, null if the component does not exist.
-     * @see hasComponent()
-     */
-    public function getComponent($id, $load = true)
-    {
-        if (isset($this->_components[$id])) {
-            if ($this->_components[$id] instanceof Object) {
-                return $this->_components[$id];
-            } elseif ($load) {
-                return $this->_components[$id] = Yii::createObject($this->_components[$id]);
-            }
-        }
-
-        return null;
-    }
-
-    /**
-     * Registers a component with this module.
-     * @param string               $id        component ID
-     * @param Component|array|null $component the component to be registered with the module. This can
-     *                                        be one of the followings:
-     *
-     * - a [[Component]] object
-     * - a configuration array: when [[getComponent()]] is called initially for this component, the array
-     *   will be used to instantiate the component via [[Yii::createObject()]].
-     * - null: the named component will be removed from the module
-     */
-    public function setComponent($id, $component)
-    {
-        if ($component === null) {
-            unset($this->_components[$id]);
-        } else {
-            $this->_components[$id] = $component;
-        }
-    }
-
-    /**
-     * Returns the registered components.
-     * @param  boolean $loadedOnly whether to return the loaded components only. If this is set false,
-     *                             then all components specified in the configuration will be returned, whether they are loaded or not.
-     *                             Loaded components will be returned as objects, while unloaded components as configuration arrays.
-     * @return array   the components (indexed by their IDs)
-     */
-    public function getComponents($loadedOnly = false)
-    {
-        if ($loadedOnly) {
-            $components = [];
-            foreach ($this->_components as $component) {
-                if ($component instanceof Component) {
-                    $components[] = $component;
-                }
-            }
-
-            return $components;
-        } else {
-            return $this->_components;
-        }
-    }
-
-    /**
-     * Registers a set of components in this module.
-     *
-     * Each component should be specified as a name-value pair, where
-     * name refers to the ID of the component and value the component or a configuration
-     * array that can be used to create the component. In the latter case, [[Yii::createObject()]]
-     * will be used to create the component.
-     *
-     * If a new component has the same ID as an existing one, the existing one will be overwritten silently.
-     *
-     * The following is an example for setting two components:
-     *
-     * ~~~
-     * [
-     *     'db' => [
-     *         'class' => 'yii\db\Connection',
-     *         'dsn' => 'sqlite:path/to/file.db',
-     *     ],
-     *     'cache' => [
-     *         'class' => 'yii\caching\DbCache',
-     *         'db' => 'db',
-     *     ],
-     * ]
-     * ~~~
-     *
-     * @param array $components components (id => component configuration or instance)
-     */
-    public function setComponents($components)
-    {
-        foreach ($components as $id => $component) {
-            if (!is_object($component) && isset($this->_components[$id]['class']) && !isset($component['class'])) {
-                // set default component class
-                $component['class'] = $this->_components[$id]['class'];
-            }
-            $this->_components[$id] = $component;
-        }
-    }
-
-    /**
      * Loads components that are declared in [[preload]].
      * @throws InvalidConfigException if a component or module to be preloaded is unknown
      */
     public function preloadComponents()
     {
         foreach ($this->preload as $id) {
-            if ($this->hasComponent($id)) {
-                $this->getComponent($id);
+            if ($this->has($id)) {
+                $this->get($id);
             } elseif ($this->hasModule($id)) {
                 $this->getModule($id);
             } else {
@@ -635,7 +489,7 @@ class Module extends Component
             return $module->createController($route);
         }
         if (isset($this->controllerMap[$id])) {
-            $controller = Yii::createObject($this->controllerMap[$id], $id, $this);
+            $controller = Yii::createObject($this->controllerMap[$id], [$id, $this]);
 
             return [$controller, $route];
         }

framework/caching/DbCache.php

@@ -11,6 +11,7 @@ use Yii;
 use yii\base\InvalidConfigException;
 use yii\db\Connection;
 use yii\db\Query;
+use yii\di\Instance;
 
 /**
  * DbCache implements a cache application component by storing cached data in a database.
@@ -79,12 +80,7 @@ class DbCache extends Cache
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException("DbCache::db must be either a DB connection instance or the application component ID of a DB connection.");
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 
     /**

framework/caching/DbDependency.php

@@ -10,6 +10,7 @@ namespace yii\caching;
 use Yii;
 use yii\base\InvalidConfigException;
 use yii\db\Connection;
+use yii\di\Instance;
 
 /**
  * DbDependency represents a dependency based on the query result of a SQL statement.
@@ -45,10 +46,7 @@ class DbDependency extends Dependency
      */
     protected function generateDependencyData($cache)
     {
-        $db = Yii::$app->getComponent($this->db);
-        if (!$db instanceof Connection) {
-            throw new InvalidConfigException("DbDependency::db must be the application component ID of a DB connection.");
-        }
+        $db = Instance::ensure($this->db, Connection::className());
         if ($this->sql === null) {
             throw new InvalidConfigException("DbDependency::sql must be set.");
         }

framework/console/Application.php

@@ -154,7 +154,7 @@ class Application extends \yii\base\Application
      */
     public function getResponse()
     {
-        return $this->getComponent('response');
+        return $this->get('response');
     }
 
     /**
@@ -193,15 +193,13 @@ class Application extends \yii\base\Application
     }
 
     /**
-     * Registers the core application components.
-     * @see setComponents
+     * @inheritdoc
      */
-    public function registerCoreComponents()
+    public function coreComponents()
     {
-        parent::registerCoreComponents();
-        $this->setComponents([
+        return array_merge([
             'request' => ['class' => 'yii\console\Request'],
             'response' => ['class' => 'yii\console\Response'],
-        ]);
+        ], parent::coreComponents());
     }
 }

framework/console/controllers/CacheController.php

@@ -53,7 +53,7 @@ class CacheController extends Controller
     public function actionFlush($component = 'cache')
     {
         /** @var Cache $cache */
-        $cache = Yii::$app->getComponent($component);
+        $cache = Yii::$app->get($component, false);
         if (!$cache || !$cache instanceof Cache) {
             throw new Exception('Application component "'.$component.'" is not defined or not a cache.');
         }

framework/console/controllers/MessageController.php

@@ -129,7 +129,7 @@ class MessageController extends Controller
                 }
             }
         } elseif ($config['format'] === 'db') {
-            $db = \Yii::$app->getComponent(isset($config['db']) ? $config['db'] : 'db');
+            $db = \Yii::$app->get(isset($config['db']) ? $config['db'] : 'db');
             if (!$db instanceof \yii\db\Connection) {
                 throw new Exception('The "db" option must refer to a valid database application component.');
             }

framework/console/controllers/MigrateController.php

@@ -122,7 +122,7 @@ class MigrateController extends Controller
 
             if ($action->id !== 'create') {
                 if (is_string($this->db)) {
-                    $this->db = Yii::$app->getComponent($this->db);
+                    $this->db = Yii::$app->get($this->db);
                 }
                 if (!$this->db instanceof Connection) {
                     throw new Exception("The 'db' option must refer to the application component ID of a DB connection.");

framework/data/ActiveDataProvider.php

@@ -13,6 +13,7 @@ use yii\base\InvalidConfigException;
 use yii\base\Model;
 use yii\db\Connection;
 use yii\db\QueryInterface;
+use yii\di\Instance;
 
 /**
  * ActiveDataProvider implements a data provider based on [[\yii\db\Query]] and [[\yii\db\ActiveQuery]].
@@ -85,10 +86,7 @@ class ActiveDataProvider extends BaseDataProvider
     {
         parent::init();
         if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-            if ($this->db === null) {
-                throw new InvalidConfigException('The "db" property must be a valid DB Connection application component.');
-            }
+            $this->db = Instance::ensure($this->db, Connection::className());
         }
     }
 

framework/data/SqlDataProvider.php

@@ -10,6 +10,7 @@ namespace yii\data;
 use Yii;
 use yii\base\InvalidConfigException;
 use yii\db\Connection;
+use yii\di\Instance;
 
 /**
  * SqlDataProvider implements a data provider based on a plain SQL statement.
@@ -89,12 +90,7 @@ class SqlDataProvider extends BaseDataProvider
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException('The "db" property must be a valid DB Connection application component.');
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
         if ($this->sql === null) {
             throw new InvalidConfigException('The "sql" property must be set.');
         }

framework/db/Command.php

@@ -378,7 +378,7 @@ class Command extends \yii\base\Component
 
         /** @var \yii\caching\Cache $cache */
         if ($db->enableQueryCache && $method !== '') {
-            $cache = is_string($db->queryCache) ? Yii::$app->getComponent($db->queryCache) : $db->queryCache;
+            $cache = is_string($db->queryCache) ? Yii::$app->get($db->queryCache, false) : $db->queryCache;
         }
 
         if (isset($cache) && $cache instanceof Cache) {

framework/db/Migration.php

@@ -6,6 +6,7 @@
  */
 
 namespace yii\db;
+use yii\di\Instance;
 
 /**
  * Migration is the base class for representing a database migration.
@@ -36,10 +37,10 @@ namespace yii\db;
 class Migration extends \yii\base\Component
 {
     /**
-     * @var Connection the database connection that this migration should work with.
-     * If not set, it will be initialized as the 'db' application component.
+     * @var Connection|string the DB connection object or the application component ID of the DB connection
+     * that this migration should work with.
      */
-    public $db;
+    public $db = 'db';
 
     /**
      * Initializes the migration.
@@ -48,9 +49,7 @@ class Migration extends \yii\base\Component
     public function init()
     {
         parent::init();
-        if ($this->db === null) {
-            $this->db = \Yii::$app->getComponent('db');
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 
     /**

framework/db/Schema.php

@@ -96,7 +96,7 @@ abstract class Schema extends Object
 
         if ($db->enableSchemaCache && !in_array($name, $db->schemaCacheExclude, true)) {
             /** @var Cache $cache */
-            $cache = is_string($db->schemaCache) ? Yii::$app->getComponent($db->schemaCache) : $db->schemaCache;
+            $cache = is_string($db->schemaCache) ? Yii::$app->get($db->schemaCache, false) : $db->schemaCache;
             if ($cache instanceof Cache) {
                 $key = $this->getCacheKey($name);
                 if ($refresh || ($table = $cache->get($key)) === false) {
@@ -225,7 +225,7 @@ abstract class Schema extends Object
     public function refresh()
     {
         /** @var Cache $cache */
-        $cache = is_string($this->db->schemaCache) ? Yii::$app->getComponent($this->db->schemaCache) : $this->db->schemaCache;
+        $cache = is_string($this->db->schemaCache) ? Yii::$app->get($this->db->schemaCache, false) : $this->db->schemaCache;
         if ($this->db->enableSchemaCache && $cache instanceof Cache) {
             GroupDependency::invalidate($cache, $this->getCacheGroup());
         }

framework/di/Instance.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\di;
+
+use Yii;
+use yii\base\InvalidConfigException;
+
+/**
+ * Instance represents a reference to a named object in a dependency injection (DI) container or a service locator.
+ *
+ * You may use [[get()]] to obtain the actual object referenced by [[id]].
+ *
+ * Instance is mainly used in two places:
+ *
+ * - When configuring a dependency injection container, you use Instance to reference a class name, interface name
+ *   or alias name. The reference can later be resolved into the actual object by the container.
+ * - In classes which use service locator to obtain dependent objects.
+ *
+ * The following example shows how to configure a DI container with Instance:
+ *
+ * ```php
+ * $container = new \yii\di\Container;
+ * $container->set('cache', 'yii\caching\DbCache', Instance::of('db'));
+ * $container->set('db', [
+ *     'class' => 'yii\db\Connection',
+ *     'dsn' => 'sqlite:path/to/file.db',
+ * ]);
+ * ```
+ *
+ * And the following example shows how a class retrieves a component from a service locator:
+ *
+ * ```php
+ * class DbCache extends Cache
+ * {
+ *     public $db = 'db';
+ *
+ *     public function init()
+ *     {
+ *         parent::init();
+ *         $this->db = Instance::ensure($this->db, 'yii\db\Connection');
+ *     }
+ * }
+ * ```
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class Instance
+{
+    /**
+     * @var string the component ID, class name, interface name or alias name
+     */
+    public $id;
+
+    /**
+     * Constructor.
+     * @param string $id the component ID
+     */
+    protected function __construct($id)
+    {
+        $this->id = $id;
+    }
+
+    /**
+     * Creates a new Instance object.
+     * @param string $id the component ID
+     * @return Instance the new Instance object.
+     */
+    public static function of($id)
+    {
+        return new static($id);
+    }
+
+    /**
+     * Resolves the specified reference into the actual object and makes sure it is of the specified type.
+     *
+     * The reference may be specified as a string or an Instance object. If the former,
+     * it will be treated as a component ID, a class/interface name or an alias, depending on the container type.
+     *
+     * If you do not specify a container, the method will first try `Yii::$app` followed by `Yii::$container`.
+     *
+     * For example,
+     *
+     * ```php
+     * use yii\db\Connection;
+     *
+     * // returns Yii::$app->db
+     * $db = Instance::ensure('db', Connection::className());
+     * // or
+     * $instance = Instance::of('db');
+     * $db = Instance::ensure($instance, Connection::className());
+     * ```
+     *
+     * @param object|string|static $reference an object or a reference to the desired object.
+     * You may specify a reference in terms of a component ID or an Instance object.
+     * @param string $type the class/interface name to be checked. If null, type check will not be performed.
+     * @param ServiceLocator|Container $container the container. This will be passed to [[get()]].
+     * @return object the object referenced by the Instance, or `$reference` itself if it is an object.
+     * @throws InvalidConfigException if the reference is invalid
+     */
+    public static function ensure($reference, $type = null, $container = null)
+    {
+        if ($reference instanceof $type) {
+            return $reference;
+        } elseif (empty($reference)) {
+            throw new InvalidConfigException('The required component is not specified.');
+        }
+
+        if (is_string($reference)) {
+            $reference = new static($reference);
+        }
+
+        if ($reference instanceof self) {
+            $component = $reference->get($container);
+            if ($component instanceof $type || $type === null) {
+                return $component;
+            } else {
+                throw new InvalidConfigException('"' . $reference->id . '" refers to a ' . get_class($component) . " component. $type is expected.");
+            }
+        }
+
+        $valueType = is_object($reference) ? get_class($reference) : gettype($reference);
+        throw new InvalidConfigException("Invalid data type: $valueType. $type is expected.");
+    }
+
+    /**
+     * Returns the actual object referenced by this Instance object.
+     * @param ServiceLocator|Container $container the container used to locate the referenced object.
+     * If null, the method will first try `Yii::$app` then `Yii::$container`.
+     * @return object the actual object referenced by this Instance object.
+     */
+    public function get($container = null)
+    {
+        if ($container) {
+            return $container->get($this->id);
+        }
+        if (Yii::$app && Yii::$app->has($this->id)) {
+            return Yii::$app->get($this->id);
+        } else {
+            return Yii::$container->get($this->id);
+        }
+    }
+}

framework/di/ServiceLocator.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\di;
+
+use Yii;
+use Closure;
+use yii\base\Component;
+use yii\base\InvalidConfigException;
+
+/**
+ * ServiceLocator implements a [service locator](http://en.wikipedia.org/wiki/Service_locator_pattern).
+ *
+ * To use ServiceLocator, you first need to register component IDs with the corresponding component
+ * definitions with the locator by calling [[set()]] or [[setComponents()]].
+ * You can then call [[get()]] to retrieve a component with the specified ID. The locator will automatically
+ * instantiate and configure the component according to the definition.
+ *
+ * For example,
+ *
+ * ```php
+ * $locator = new \yii\di\ServiceLocator;
+ * $locator->setComponents([
+ *     'db' => [
+ *         'class' => 'yii\db\Connection',
+ *         'dsn' => 'sqlite:path/to/file.db',
+ *     ],
+ *     'cache' => [
+ *         'class' => 'yii\caching\DbCache',
+ *         'db' => 'db',
+ *     ],
+ * ]);
+ *
+ * $db = $locator->get('db');  // or $locator->db
+ * $cache = $locator->get('cache');  // or $locator->cache
+ * ```
+ *
+ * Because [[\yii\base\Module]] extends from ServiceLocator, modules and the application are all service locators.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class ServiceLocator extends Component
+{
+    /**
+     * @var array shared component instances indexed by their IDs
+     */
+    private $_components = [];
+    /**
+     * @var array component definitions indexed by their IDs
+     */
+    private $_definitions = [];
+
+
+    /**
+     * Getter magic method.
+     * This method is overridden to support accessing components like reading properties.
+     * @param  string $name component or property name
+     * @return mixed  the named property value
+     */
+    public function __get($name)
+    {
+        if ($this->has($name)) {
+            return $this->get($name);
+        } else {
+            return parent::__get($name);
+        }
+    }
+
+    /**
+     * Checks if a property value is null.
+     * This method overrides the parent implementation by checking if the named component is loaded.
+     * @param  string  $name the property name or the event name
+     * @return boolean whether the property value is null
+     */
+    public function __isset($name)
+    {
+        if ($this->has($name, true)) {
+            return true;
+        } else {
+            return parent::__isset($name);
+        }
+    }
+
+    /**
+     * Returns a value indicating whether the locator has the specified component definition or has instantiated the component.
+     * This method may return different results depending on the value of `$checkInstance`.
+     *
+     * - If `$checkInstance` is false (default), the method will return a value indicating whether the locator has the specified
+     *   component definition.
+     * - If `$checkInstance` is true, the method will return a value indicating whether the locator has
+     *   instantiated the specified component.
+     *
+     * @param string $id component ID (e.g. `db`).
+     * @param boolean $checkInstance whether the method should check if the component is shared and instantiated.
+     * @return boolean whether the locator has the specified component definition or has instantiated the component.
+     * @see set()
+     */
+    public function has($id, $checkInstance = false)
+    {
+        return $checkInstance ? isset($this->_components[$id]) : isset($this->_definitions[$id]);
+    }
+
+    /**
+     * Returns the component instance with the specified ID.
+     *
+     * @param string $id component ID (e.g. `db`).
+     * @param boolean $throwException whether to throw an exception if `$id` is not registered with the locator before.
+     * @return object|null the component of the specified ID. If `$throwException` is false and `$id`
+     * is not registered before, null will be returned.
+     * @throws InvalidConfigException if `$id` refers to a nonexistent component ID
+     * @see has()
+     * @see set()
+     */
+    public function get($id, $throwException = true)
+    {
+        if (isset($this->_components[$id])) {
+            return $this->_components[$id];
+        }
+
+        if (isset($this->_definitions[$id])) {
+            $definition = $this->_definitions[$id];
+            if (is_object($definition) && !$definition instanceof Closure) {
+                return $this->_components[$id] = $definition;
+            } else {
+                return $this->_components[$id] = Yii::createObject($definition);
+            }
+        } elseif ($throwException) {
+            throw new InvalidConfigException("Unknown component ID: $id");
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Registers a component definition with this locator.
+     *
+     * For example,
+     *
+     * ```php
+     * // a class name
+     * $locator->set('cache', 'yii\caching\FileCache');
+     *
+     * // a configuration array
+     * $locator->set('db', [
+     *     'class' => 'yii\db\Connection',
+     *     'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
+     *     'username' => 'root',
+     *     'password' => '',
+     *     'charset' => 'utf8',
+     * ]);
+     *
+     * // an anonymous function
+     * $locator->set('cache', function ($params) {
+     *     return new \yii\caching\FileCache;
+     * });
+     *
+     * // an instance
+     * $locator->set('cache', new \yii\caching\FileCache);
+     * ```
+     *
+     * If a component definition with the same ID already exists, it will be overwritten.
+     *
+     * @param string $id component ID (e.g. `db`).
+     * @param mixed $definition the component definition to be registered with this locator.
+     * It can be one of the followings:
+     *
+     * - a class name
+     * - a configuration array: the array contains name-value pairs that will be used to
+     *   initialize the property values of the newly created object when [[get()]] is called.
+     *   The `class` element is required and stands for the the class of the object to be created.
+     * - a PHP callable: either an anonymous function or an array representing a class method (e.g. `['Foo', 'bar']`).
+     *   The callable will be called by [[get()]] to return an object associated with the specified component ID.
+     * - an object: When [[get()]] is called, this object will be returned.
+     *
+     * @throws InvalidConfigException if the definition is an invalid configuration array
+     */
+    public function set($id, $definition)
+    {
+        if ($definition === null) {
+            unset($this->_components[$id], $this->_definitions[$id]);
+            return;
+        }
+
+        if (is_object($definition) || is_callable($definition, true)) {
+            // an object, a class name, or a PHP callable
+            $this->_definitions[$id] = $definition;
+        } elseif (is_array($definition)) {
+            // a configuration array
+            if (isset($definition['class'])) {
+                $this->_definitions[$id] = $definition;
+            } else {
+                throw new InvalidConfigException("The configuration for the \"$id\" component must contain a \"class\" element.");
+            }
+        } else {
+            throw new InvalidConfigException("Unexpected configuration type for the \"$id\" component: " . gettype($definition));
+        }
+    }
+
+    /**
+     * Removes the component from the locator.
+     * @param string $id the component ID
+     */
+    public function clear($id)
+    {
+        unset($this->_definitions[$id], $this->_components[$id]);
+    }
+
+    /**
+     * Returns the list of the component definitions or the loaded component instances.
+     * @param boolean $returnDefinitions whether to return component definitions instead of the loaded component instances.
+     * @return array the list of the component definitions or the loaded component instances (ID => definition or instance).
+     */
+    public function getComponents($returnDefinitions = true)
+    {
+        return $returnDefinitions ? $this->_definitions : $this->_components;
+    }
+
+    /**
+     * Registers a set of component definitions in this locator.
+     *
+     * This is the bulk version of [[set()]]. The parameter should be an array
+     * whose keys are component IDs and values the corresponding component definitions.
+     *
+     * For more details on how to specify component IDs and definitions, please refer to [[set()]].
+     *
+     * If a component definition with the same ID already exists, it will be overwritten.
+     *
+     * The following is an example for registering two component definitions:
+     *
+     * ```php
+     * [
+     *     'db' => [
+     *         'class' => 'yii\db\Connection',
+     *         'dsn' => 'sqlite:path/to/file.db',
+     *     ],
+     *     'cache' => [
+     *         'class' => 'yii\caching\DbCache',
+     *         'db' => 'db',
+     *     ],
+     * ]
+     * ```
+     *
+     * @param array $components component definitions or instances
+     */
+    public function setComponents($components)
+    {
+        foreach ($components as $id => $component) {
+            $this->set($id, $component);
+        }
+    }
+}

framework/i18n/DbMessageSource.php

@@ -9,6 +9,7 @@ namespace yii\i18n;
 
 use Yii;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 use yii\helpers\ArrayHelper;
 use yii\caching\Cache;
 use yii\db\Connection;
@@ -93,19 +94,9 @@ class DbMessageSource extends MessageSource
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException("DbMessageSource::db must be either a DB connection instance or the application component ID of a DB connection.");
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
         if ($this->enableCaching) {
-            if (is_string($this->cache)) {
-                $this->cache = Yii::$app->getComponent($this->cache);
-            }
-            if (!$this->cache instanceof Cache) {
-                throw new InvalidConfigException("DbMessageSource::cache must be either a cache object or the application component ID of the cache object.");
-            }
+            $this->cache = Instance::ensure($this->cache, Cache::className());
         }
     }
 

framework/log/DbTarget.php

@@ -10,6 +10,7 @@ namespace yii\log;
 use Yii;
 use yii\db\Connection;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 
 /**
  * DbTarget stores log messages in a database table.
@@ -62,12 +63,7 @@ class DbTarget extends Target
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException("DbTarget::db must be either a DB connection instance or the application component ID of a DB connection.");
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 
     /**

framework/log/EmailTarget.php

@@ -9,6 +9,7 @@ namespace yii\log;
 
 use Yii;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 use yii\mail\MailerInterface;
 
 /**
@@ -43,12 +44,7 @@ class EmailTarget extends Target
         if (empty($this->message['to'])) {
             throw new InvalidConfigException('The "to" option must be set for EmailTarget::message.');
         }
-        if (is_string($this->mail)) {
-            $this->mail = Yii::$app->getComponent($this->mail);
-        }
-        if (!$this->mail instanceof MailerInterface) {
-            throw new InvalidConfigException("EmailTarget::mailer must be either a mailer object or the application component ID of a mailer object.");
-        }
+        $this->mail = Instance::ensure($this->mail, 'yii\mail\MailerInterface');
     }
 
     /**

framework/log/Target.php

@@ -247,10 +247,10 @@ abstract class Target extends Component
         $request = Yii::$app->getRequest();
         $ip = $request instanceof Request ? $request->getUserIP() : '-';
         /** @var \yii\web\User $user */
-        $user = Yii::$app->getComponent('user', false);
+        $user = Yii::$app->has('user', true) ? Yii::$app->get('user') : null;
         $userID = $user ? $user->getId(false) : '-';
         /** @var \yii\web\Session $session */
-        $session = Yii::$app->getComponent('session', false);
+        $session = Yii::$app->has('session', true) ? Yii::$app->get('session') : null;
         $sessionID = $session && $session->getIsActive() ? $session->getId() : '-';
         return "[$ip] [$userID] [$sessionID]";
     }

framework/mutex/DbMutex.php

@@ -10,6 +10,7 @@ namespace yii\mutex;
 use Yii;
 use yii\db\Connection;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 
 /**
  * @author resurtm <resurtm@gmail.com>
@@ -31,11 +32,6 @@ abstract class DbMutex extends Mutex
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException('Mutex::db must be either a DB connection instance or the application component ID of a DB connection.');
-        }
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 }

framework/rbac/DbManager.php

@@ -15,6 +15,7 @@ use yii\base\Exception;
 use yii\base\InvalidConfigException;
 use yii\base\InvalidCallException;
 use yii\base\InvalidParamException;
+use yii\di\Instance;
 
 /**
  * DbManager represents an authorization manager that stores authorization information in database.
@@ -59,14 +60,9 @@ class DbManager extends Manager
      */
     public function init()
     {
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException("DbManager::db must be either a DB connection instance or the application component ID of a DB connection.");
-        }
-        $this->_usingSqlite = !strncmp($this->db->getDriverName(), 'sqlite', 6);
         parent::init();
+        $this->db = Instance::ensure($this->db, Connection::className());
+        $this->_usingSqlite = !strncmp($this->db->getDriverName(), 'sqlite', 6);
     }
 
     /**

framework/test/DbFixture.php

@@ -10,6 +10,8 @@ namespace yii\test;
 use Yii;
 use yii\base\InvalidConfigException;
 use yii\db\Connection;
+use yii\di\Instance;
+use yii\base\Object;
 
 /**
  * DbFixture is the base class for DB-related fixtures.
@@ -34,11 +36,6 @@ abstract class DbFixture extends Fixture
     public function init()
     {
         parent::init();
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!is_object($this->db)) {
-            throw new InvalidConfigException("The 'db' property must be either a DB connection instance or the application component ID of a DB connection.");
-        }
+        $this->db = Instance::ensure($this->db, Object::className());
     }
 }

framework/web/Application.php

@@ -129,7 +129,7 @@ class Application extends \yii\base\Application
      */
     public function getRequest()
     {
-        return $this->getComponent('request');
+        return $this->get('request');
     }
 
     /**
@@ -138,7 +138,7 @@ class Application extends \yii\base\Application
      */
     public function getResponse()
     {
-        return $this->getComponent('response');
+        return $this->get('response');
     }
 
     /**
@@ -147,7 +147,7 @@ class Application extends \yii\base\Application
      */
     public function getSession()
     {
-        return $this->getComponent('session');
+        return $this->get('session');
     }
 
     /**
@@ -156,7 +156,7 @@ class Application extends \yii\base\Application
      */
     public function getUser()
     {
-        return $this->getComponent('user');
+        return $this->get('user');
     }
 
     /**
@@ -165,22 +165,20 @@ class Application extends \yii\base\Application
      */
     public function getAssetManager()
     {
-        return $this->getComponent('assetManager');
+        return $this->get('assetManager');
     }
 
     /**
-     * Registers the core application components.
-     * @see setComponents
+     * @inheritdoc
      */
-    public function registerCoreComponents()
+    public function coreComponents()
     {
-        parent::registerCoreComponents();
-        $this->setComponents([
+        return array_merge([
             'request' => ['class' => 'yii\web\Request'],
             'response' => ['class' => 'yii\web\Response'],
             'session' => ['class' => 'yii\web\Session'],
             'user' => ['class' => 'yii\web\User'],
             'assetManager' => ['class' => 'yii\web\AssetManager'],
-        ]);
+        ], parent::coreComponents());
     }
 }

framework/web/CacheSession.php

@@ -10,6 +10,7 @@ namespace yii\web;
 use Yii;
 use yii\caching\Cache;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 
 /**
  * CacheSession implements a session component using cache as storage medium.
@@ -52,13 +53,8 @@ class CacheSession extends Session
      */
     public function init()
     {
-        if (is_string($this->cache)) {
-            $this->cache = Yii::$app->getComponent($this->cache);
-        }
-        if (!$this->cache instanceof Cache) {
-            throw new InvalidConfigException('CacheSession::cache must refer to the application component ID of a cache object.');
-        }
         parent::init();
+        $this->cache = Instance::ensure($this->cache, Cache::className());
     }
 
     /**

framework/web/DbSession.php

@@ -11,6 +11,7 @@ use Yii;
 use yii\db\Connection;
 use yii\db\Query;
 use yii\base\InvalidConfigException;
+use yii\di\Instance;
 
 /**
  * DbSession extends [[Session]] by using database as session data storage.
@@ -74,13 +75,8 @@ class DbSession extends Session
      */
     public function init()
     {
-        if (is_string($this->db)) {
-            $this->db = Yii::$app->getComponent($this->db);
-        }
-        if (!$this->db instanceof Connection) {
-            throw new InvalidConfigException("DbSession::db must be either a DB connection instance or the application component ID of a DB connection.");
-        }
         parent::init();
+        $this->db = Instance::ensure($this->db, Connection::className());
     }
 
     /**

framework/web/UrlManager.php

@@ -145,7 +145,7 @@ class UrlManager extends Component
             return;
         }
         if (is_string($this->cache)) {
-            $this->cache = Yii::$app->getComponent($this->cache);
+            $this->cache = Yii::$app->get($this->cache, false);
         }
         if ($this->cache instanceof Cache) {
             $key = __CLASS__;

framework/widgets/FragmentCache.php

@@ -11,6 +11,7 @@ use Yii;
 use yii\base\Widget;
 use yii\caching\Cache;
 use yii\caching\Dependency;
+use yii\di\Instance;
 
 /**
  *
@@ -79,11 +80,7 @@ class FragmentCache extends Widget
     {
         parent::init();
 
-        if (!$this->enabled) {
-            $this->cache = null;
-        } elseif (is_string($this->cache)) {
-            $this->cache = Yii::$app->getComponent($this->cache);
-        }
+        $this->cache = $this->enabled ? Instance::ensure($this->cache, Cache::className()) : null;
 
         if ($this->getCachedContent() === false) {
             $this->getView()->cacheStack[] = $this;

tests/unit/extensions/swiftmailer/MessageTest.php

@@ -68,7 +68,7 @@ class MessageTest extends VendorTestCase
      */
     protected function createTestMessage()
     {
-        return Yii::$app->getComponent('mail')->compose();
+        return Yii::$app->get('mail')->compose();
     }
 
     /**

tests/unit/framework/di/ContainerTest.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di;
+
+use yii\di\Container;
+use yii\di\Instance;
+use yiiunit\framework\di\stubs\Bar;
+use yiiunit\framework\di\stubs\Foo;
+use yiiunit\framework\di\stubs\Qux;
+use yiiunit\TestCase;
+
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class ContainerTest extends TestCase
+{
+    public function testDefault()
+    {
+        $namespace = __NAMESPACE__ . '\stubs';
+        $QuxInterface = "$namespace\\QuxInterface";
+        $Foo = Foo::className();
+        $Bar = Bar::className();
+        $Qux = Qux::className();
+
+        // automatic wiring
+        $container = new Container;
+        $container->set($QuxInterface, $Qux);
+        $foo = $container->get($Foo);
+        $this->assertTrue($foo instanceof $Foo);
+        $this->assertTrue($foo->bar instanceof $Bar);
+        $this->assertTrue($foo->bar->qux instanceof $Qux);
+
+        // full wiring
+        $container = new Container;
+        $container->set($QuxInterface, $Qux);
+        $container->set($Bar);
+        $container->set($Qux);
+        $container->set($Foo);
+        $foo = $container->get($Foo);
+        $this->assertTrue($foo instanceof $Foo);
+        $this->assertTrue($foo->bar instanceof $Bar);
+        $this->assertTrue($foo->bar->qux instanceof $Qux);
+
+        // wiring by closure
+        $container = new Container;
+        $container->set('foo', function () {
+            $qux = new Qux;
+            $bar = new Bar($qux);
+            return new Foo($bar);
+        });
+        $foo = $container->get('foo');
+        $this->assertTrue($foo instanceof $Foo);
+        $this->assertTrue($foo->bar instanceof $Bar);
+        $this->assertTrue($foo->bar->qux instanceof $Qux);
+
+        // wiring by closure which uses container
+        $container = new Container;
+        $container->set($QuxInterface, $Qux);
+        $container->set('foo', function (Container $c, $params, $config) {
+            return $c->get(Foo::className());
+        });
+        $foo = $container->get('foo');
+        $this->assertTrue($foo instanceof $Foo);
+        $this->assertTrue($foo->bar instanceof $Bar);
+        $this->assertTrue($foo->bar->qux instanceof $Qux);
+
+        // predefined constructor parameters
+        $container = new Container;
+        $container->set('foo', $Foo, [Instance::of('bar')]);
+        $container->set('bar', $Bar, [Instance::of('qux')]);
+        $container->set('qux', $Qux);
+        $foo = $container->get('foo');
+        $this->assertTrue($foo instanceof $Foo);
+        $this->assertTrue($foo->bar instanceof $Bar);
+        $this->assertTrue($foo->bar->qux instanceof $Qux);
+    }
+}

tests/unit/framework/di/InstanceTest.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di;
+
+use yii\base\Component;
+use yii\di\Container;
+use yii\di\Instance;
+use yiiunit\TestCase;
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class InstanceTest extends TestCase
+{
+    public function testOf()
+    {
+        $container = new Container;
+        $className = Component::className();
+        $instance = Instance::of($className, $container);
+        $this->assertTrue($instance instanceof Instance);
+        $this->assertTrue($instance->get() instanceof Component);
+        $this->assertTrue(Instance::ensure($instance, $className) instanceof Component);
+        $this->assertTrue($instance->get() !== Instance::ensure($instance, $className));
+    }
+}

tests/unit/framework/di/ServiceLocatorTest.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di;
+
+use yii\base\Object;
+use yii\di\ServiceLocator;
+use yiiunit\TestCase;
+
+class Creator
+{
+    public static function create()
+    {
+        return new TestClass;
+    }
+}
+
+class TestClass extends Object
+{
+    public $prop1 = 1;
+    public $prop2;
+}
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class ServiceLocatorTest extends TestCase
+{
+    public function testCallable()
+    {
+        // anonymous function
+        $container = new ServiceLocator;
+        $className = TestClass::className();
+        $container->set($className, function () {
+            return new TestClass([
+                'prop1' => 100,
+                'prop2' => 200,
+            ]);
+        });
+        $object = $container->get($className);
+        $this->assertTrue($object instanceof $className);
+        $this->assertEquals(100, $object->prop1);
+        $this->assertEquals(200, $object->prop2);
+
+        // static method
+        $container = new ServiceLocator;
+        $className = TestClass::className();
+        $container->set($className, [__NAMESPACE__ . "\\Creator", 'create']);
+        $object = $container->get($className);
+        $this->assertTrue($object instanceof $className);
+        $this->assertEquals(1, $object->prop1);
+        $this->assertNull($object->prop2);
+    }
+
+    public function testObject()
+    {
+        $object = new TestClass;
+        $className = TestClass::className();
+        $container = new ServiceLocator;
+        $container->set($className, $object);
+        $this->assertTrue($container->get($className) === $object);
+    }
+
+    public function testShared()
+    {
+        // with configuration: shared
+        $container = new ServiceLocator;
+        $className = TestClass::className();
+        $container->set($className, [
+            'class' => $className,
+            'prop1' => 10,
+            'prop2' => 20,
+        ]);
+        $object = $container->get($className);
+        $this->assertEquals(10, $object->prop1);
+        $this->assertEquals(20, $object->prop2);
+        $this->assertTrue($object instanceof $className);
+        // check shared
+        $object2 = $container->get($className);
+        $this->assertTrue($object2 instanceof $className);
+        $this->assertTrue($object === $object2);
+    }
+}

tests/unit/framework/di/stubs/Bar.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di\stubs;
+
+use yii\base\Object;
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class Bar extends Object
+{
+    public $qux;
+
+    public function __construct(QuxInterface $qux, $config = [])
+    {
+        $this->qux = $qux;
+        parent::__construct($config);
+    }
+}

tests/unit/framework/di/stubs/Foo.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di\stubs;
+
+use yii\base\Object;
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class Foo extends Object
+{
+    public $bar;
+
+    public function __construct(Bar $bar, $config = [])
+    {
+        $this->bar = $bar;
+        parent::__construct($config);
+    }
+}

tests/unit/framework/di/stubs/Qux.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di\stubs;
+
+use yii\base\Object;
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class Qux extends Object implements QuxInterface
+{
+    public $a;
+
+    public function __construct($a = 1, $config = [])
+    {
+        $this->a = $a;
+        parent::__construct($config);
+    }
+
+    public function quxMethod()
+    {
+    }
+}

tests/unit/framework/di/stubs/QuxInterface.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\di\stubs;
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+interface QuxInterface
+{
+    function quxMethod();
+}

tests/unit/framework/mail/BaseMailerTest.php

@@ -59,7 +59,7 @@ class BaseMailerTest extends TestCase
      */
     protected function getTestMailComponent()
     {
-        return Yii::$app->getComponent('mail');
+        return Yii::$app->get('mail');
     }
 
     // Tests :

tests/unit/framework/mail/BaseMessageTest.php

@@ -36,7 +36,7 @@ class BaseMessageTest extends TestCase
      */
     protected function getMailer()
     {
-        return Yii::$app->getComponent('mail');
+        return Yii::$app->get('mail');
     }
 
     // Tests :

tests/unit/framework/test/ActiveFixtureTest.php

@@ -58,7 +58,7 @@ class ActiveFixtureTest extends DatabaseTestCase
     public function setUp()
     {
         parent::setUp();
-        \Yii::$app->setComponent('db', $this->getConnection());
+        \Yii::$app->set('db', $this->getConnection());
         ActiveRecord::$db = $this->getConnection();
     }
 

tests/unit/framework/web/CacheSessionTest.php

@@ -15,7 +15,7 @@ class CacheSessionTest extends \yiiunit\TestCase
     {
         parent::setUp();
         $this->mockApplication();
-        Yii::$app->setComponent('cache', new FileCache());
+        Yii::$app->set('cache', new FileCache());
     }
 
     public function testCacheSession()
@@ -30,7 +30,7 @@ class CacheSessionTest extends \yiiunit\TestCase
 
     public function testInvalidCache()
     {
-        $this->setExpectedException('yii\base\InvalidConfigException');
+        $this->setExpectedException('\Exception');
         new CacheSession(['cache' => 'invalid']);
     }
 }