- Yii Tutorial
- Yii - Home
- Yii - Overview
- Yii - Installation
- Yii - Create Page
- Yii - Application Structure
- Yii - Entry Scripts
- Yii - Controllers
- Yii - Using Controllers
- Yii - Using Actions
- Yii - Models
- Yii - Widgets
- Yii - Modules
- Yii - Views
- Yii - Layouts
- Yii - Assets
- Yii - Asset Conversion
- Yii - Extensions
- Yii - Creating Extensions
- Yii - HTTP Requests
- Yii - Responses
- Yii - URL Formats
- Yii - URL Routing
- Yii - Rules of URL
- Yii - HTML Forms
- Yii - Validation
- Yii - Ad Hoc Validation
- Yii - AJAX Validation
- Yii - Sessions
- Yii - Using Flash Data
- Yii - Cookies
- Yii - Using Cookies
- Yii - Files Upload
- Yii - Formatting
- Yii - Pagination
- Yii - Sorting
- Yii - Properties
- Yii - Data Providers
- Yii - Data Widgets
- Yii - ListView Widget
- Yii - GridView Widget
- Yii - Events
- Yii - Creating Event
- Yii - Behaviors
- Yii - Creating a Behavior
- Yii - Configurations
- Yii - Dependency Injection
- Yii - Database Access
- Yii - Data Access Objects
- Yii - Query Builder
- Yii - Active Record
- Yii - Database Migration
- Yii - Theming
- Yii - RESTful APIs
- Yii - RESTful APIs in Action
- Yii - Fields
- Yii - Testing
- Yii - Caching
- Yii - Fragment Caching
- Yii - Aliases
- Yii - Logging
- Yii - Error Handling
- Yii - Authentication
- Yii - Authorization
- Yii - Localization
- Yii - Gii
- Gii – Creating a Model
- Gii – Generating Controller
- Gii – Generating Module
- Yii Useful Resources
- Yii - Quick Guide
- Yii - Useful Resources
- Yii - Discussion
Yii - Dependency Injection
A DI(dependency injection) container is an object that knows how to instantiate and configure objects. Yii provides the DI container via the yii\di\Container class.
It supports the following kinds of DI −
- Setter and property injection
- PHP callable injection
- Constructor injection
- Controller action injection
The DI container supports constructor injection with the help of type hints −
class Object1 { public function __construct(Object2 $object2) { } } $object1 = $container->get('Object1'); // which is equivalent to the following: $object2 = new Object2; $object1 = new Object1($object2);
Property and setter injections are supported through configurations −
<?php use yii\base\Object; class MyObject extends Object { public $var1; private $_var2; public function getVar2() { return $this->_var2; } public function setVar2(MyObject2 $var2) { $this->_var2 = $var2; } } $container->get('MyObject', [], [ 'var1' => $container->get('MyOtherObject'), 'var2' => $container->get('MyObject2'), ]); ?>
In case of the PHP callable injection, the container will use a registered PHP callback to build new instances of a class −
$container->set('Object1', function () { $object1 = new Object1(new Object2); return $object1; }); $object1 = $container->get('Object1');
Controller action injection is a type of DI where dependencies are declared using the type hints. It is useful for keeping the MVC controllers slim light-weighted and slim −
public function actionSendToAdmin(EmailValidator $validator, $email) { if ($validator->validate($email)) { // sending email } }
You can use the yii\db\Container::set() method to register dependencies −
<?php $container = new \yii\di\Container; // register a class name as is. This can be skipped. $container->set('yii\db\Connection'); // register an alias name. You can use $container->get('MyObject') // to create an instance of Connection $container->set('MyObject', 'yii\db\Connection'); // register an interface // When a class depends on the interface, the corresponding class // will be instantiated as the dependent object $container->set('yii\mail\MailInterface', 'yii\swiftmailer\Mailer'); // register an alias name with class configuration // In this case, a "class" element is required to specify the class $container->set('db', [ 'class' => 'yii\db\Connection', 'dsn' => 'mysql:host=127.0.0.1;dbname = helloworld', 'username' => 'vladimir', 'password' => '12345', 'charset' => 'utf8', ]); // register a class with configuration. The configuration // will be applied when the class is instantiated by get() $container->set('yii\db\Connection', [ 'dsn' => 'mysql:host=127.0.0.1;dbname = helloworld', 'username' => 'vladimir', 'password' => '12345', 'charset' => 'utf8', ]); // register a PHP callable // The callable will be executed each time when $container->get('db') is called $container->set('db', function ($container, $params, $config) { return new \yii\db\Connection($config); }); // register a component instance // $container->get('pageCache') will return the same instance each time when it //is called $container->set('pageCache', new FileCache); ?>
Using the DI
Step 1 − Inside the components folder create a file called MyInterface.php with the following code.
<?php namespace app\components; interface MyInterface { public function test(); } ?>
Step 2 − Inside the components folder, create two files.
First.php −
<?php namespace app\components; use app\components\MyInterface; class First implements MyInterface { public function test() { echo "First class <br>"; } } ?>
Second.php −
<?php app\components; use app\components\MyInterface; class Second implements MyInterface { public function test() { echo "Second class <br>"; } } ?>
Step 3 − Now, add an actionTestInterface to the SiteController.
public function actionTestInterface() { $container = new \yii\di\Container(); $container->set ("\app\components\MyInterface","\app\components\First"); $obj = $container->get("\app\components\MyInterface"); $obj->test(); // print "First class" $container->set ("\app\components\MyInterface","\app\components\Second"); $obj = $container->get("\app\components\MyInterface"); $obj->test(); // print "Second class" }
Step 4 − Go to http://localhost:8080/index.php?r=site/test-interface you should see the following.
This approach is convenient as we can set classes in one place and other code will use new classes automatically.
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