Yii2 dependency injection example - php

Question

Can someone point me in the direction of a practical example or tutorial using the DI container in Yii2?
I must be thick but the 2.0 guide on this subject is just not that clear to me. Also, most on-line tutorial and sample code I have reviewed is peppered with the Yii::$app singleton, which makes testing difficult.

Answer 1

For example you have classes \app\components\First and \app\components\Second implements one interface \app\components\MyInterface
You can use DI container to change class only in one place. For example:
class First implements MyInterface{
public function test()
{
echo "First class";
}
}
class Second implements MyInterface {
public function test()
{
echo "Second class";
}
}
$container= new \yii\di\Container();
$container->set ("\app\components\MyInterface","\app\components\First");
Now you give instance of First class when calling $container->get("\app\components\MyInterface");
$obj = $container->get("\app\components\MyInterface");
$obj->test(); // print "First class"
But now we can set other class for this interface.
$container->set ("\app\components\MyInterface","\app\components\Second");
$obj = $container->get("\app\components\MyInterface");
$obj->test(); // print "Second class"
You can set classes in one place and other code will used new class automatically.
Here you can find great documentation for this pattern in Yii with code examples.

Answer 2

this is a simple example to set default widget settings:
// Gridview default settings
$gridviewSettings = [
'export' => false,
'responsive' => true,
'floatHeader' => true,
'floatHeaderOptions' => ['scrollingTop' => 88],
'hover' => true,
'pjax' => true,
'pjaxSettings' => [
'options' => [
'id' => 'grid-pjax',
],
],
'resizableColumns' => false,
];
Yii::$container->set('kartik\grid\GridView', $gridviewSettings);

Answer 3

I have some similar requirement where I want to start new project with Yii2 because of
production readiness but eventually I would move to yii3 once it become production ready. To keep the migration easy, it is recommended from yii to replace Yii::$app with dependency injection and that's where I need to implement dependency injections for my components to be used in controllers.
Here is my component.
<?php
namespace common\services;
use Yii;
use yii\base\Component;
class HelloService extends Component
{
public function welcome() {
echo "Welcome from service component";
}
}
Here is my controller using above component and accessing it through dependency injection.
<?php
namespace console\controllers;
use yii\console\Controller;
use common\services\HelloService;
class HelloController extends Controller
{
public $message;
/** #var common\services\HelloService $helloService */
private $helloService;
public function __construct($id, $module, HelloService $helloService, $config = [])
{
$this->helloService = $helloService;
parent::__construct($id, $module, $config);
}
public function actionIndex()
{
echo $this->helloService->welcome() . "\n";
}
}