(Dependency Injection): Implement dependency injection sample in Yii2

Author: Adegoke Obasa

app/config/services.php

@@ -0,0 +1,5 @@
+<?php
+/**
+ * @author Adegoke Obasa <[email protected]>
+ */
+Yii::$container->set('app\services\DummyServiceInterface', 'app\services\DummyService');

app/controllers/SiteController.php

@@ -2,14 +2,24 @@
 
 namespace app\controllers;
 
+use app\models\ContactForm;
+use app\models\LoginForm;
+use app\services\DummyServiceInterface;
 use Yii;
 use yii\filters\AccessControl;
 use yii\filters\VerbFilter;
-use app\models\LoginForm;
-use app\models\ContactForm;
 
 class SiteController extends BaseController
 {
+    /** @var  DummyServiceInterface */
+    protected $dummyService;
+
+    public function __construct($id, $module, DummyServiceInterface $dummyService, $config = [])
+    {
+        $this->dummyService = $dummyService;
+        parent::__construct($id, $module, $config);
+    }
+
     public function behaviors()
     {
         return [
@@ -51,6 +61,11 @@ public function actionIndex()
         return $this->render('index');
     }
 
+    public function actionServiceTest()
+    {
+        return $this->dummyService->shout("Hello World");
+    }
+
     public function actionLogin()
     {
         if (!\Yii::$app->user->isGuest) {
@@ -88,8 +103,9 @@ public function actionContact()
 
     public function actionAbout()
     {
-        if($this->getUser()->isGuest)
+        if ($this->getUser()->isGuest) {
             return $this->getUser()->loginRequired();
+        }
         return $this->render('about');
     }
 }

app/services/DummyService.php

@@ -0,0 +1,16 @@
+<?php
+/**
+ * @author Adegoke Obasa <[email protected]>
+ */
+
+namespace app\services;
+
+use yii\base\Object;
+
+class DummyService extends Object implements DummyServiceInterface
+{
+    public function shout($text)
+    {
+        return $text;
+    }
+}

app/services/DummyServiceInterface.php

@@ -0,0 +1,11 @@
+<?php
+/**
+ * @author Adegoke Obasa <[email protected]>
+ */
+
+namespace app\services;
+
+interface DummyServiceInterface
+{
+    public function shout($text);
+}

app/web/index.php

@@ -17,12 +17,12 @@
 $envs = ['development', 'staging', 'production'];
 $env = getenv("APPLICATION_ENV");
 
-if(!in_array($env, $envs)) {
+if (!in_array($env, $envs)) {
     die("Environment is not valid");
 }
 
 // Only show debug toolbar and allow gii when in development
-if($env == "development") {
+if ($env == "development") {
     defined('YII_DEBUG') or define('YII_DEBUG', true);
     defined('YII_ENV') or define('YII_ENV', 'dev');
 }
@@ -32,6 +32,10 @@
 // Require configuration file
 $config = require(__DIR__ . "/../config/web.php");
 
+
+// Service Dependencies
+require(__DIR__ . "/../config/services.php");
+
 // Change this to your timezone
-ini_set( 'date.timezone', 'Africa/Lagos');
-(new yii\web\Application($config))->run();
+ini_set('date.timezone', 'Africa/Lagos');
+(new yii\web\Application($config))->run();