使用Yii2依賴注入簡化開發

本文代碼

https://github.com/xialeistudio/yii2-di-demo

什麼是依賴注入(DI)?

對象由框架來建立而不是程序員經過 new 建立。跟IoC差很少一個意思。

爲何要有依賴注入?

1. 解耦。調用方再也不經過 new 運算符實例化被調用對象，而經過框架(IoC容器)建立以後注入進來。解除了調用者與被調用者之間的依賴。
2. 有利於面向接口編程。我的認爲OOP程序設計最重要的就是面向接口(面向抽象)編程。由於有了第1步的關係，調用者只須要依賴接口類型而不用依賴實現類型，提升了程序的擴展性。

Yii2的依賴注入

Yii2經過 yiidiContainer 提供DI容器特性。目前支持一下4種方式注入：

1. 構造方法注入
2. 方法注入
3. Setter和屬性注入
4. PHP回調注入

註冊依賴關係

1. 經過容器的 set 方法注入
2. 經過配置文件注入(推薦)

依賴注入實戰

1. 打開終端，執行如下命令初始化項目：

   composer create-project --prefer-dist yiisoft/yii2-app-basic basic

2. 聲明接口業務類 appservicesUserService

   <?php
   namespace app\services;
   
   interface UserService
   {
       public function show($id);
       
       public function all();
   }

3. 接口實現文件 appservicesimplUserServiceImpl

   <?php
   namespace app\services\impl;
   
   use app\services\UserService;
   
   class UserServiceImpl implements UserService
   {
       private $users = [
           ['id' => 1, 'name' => 'xialei'],
           ['id' => 2, 'name' => 'zhangsan'],
       ];
   
       public function show($id)
       {
           foreach ($this->users as $user) {
               if ($user['id'] == $id) {
                   return $user;
               }
           }
           return null;
       }
   
       public function all()
       {
           return $this->users;
       }
   }

4. 註冊依賴關係 config/web.php

   <?php
   
   use app\services\UserService;
   use app\services\impl\UserServiceImpl;
   
   $params = require __DIR__ . '/params.php';
   $db = require __DIR__ . '/db.php';
   
   $config = [
       'id' => 'basic',
       'basePath' => dirname(__DIR__),
       'bootstrap' => ['log'],
       'aliases' => [
           '@bower' => '@vendor/bower-asset',
           '@npm' => '@vendor/npm-asset',
       ],
       'container' => [
           'definitions' => [
               UserService::class => UserServiceImpl::class
           ]
       ],
       'components' => [
           'request' => [
               // !!! insert a secret key in the following (if it is empty) - this is required by cookie validation
               'cookieValidationKey' => '0xGrStOOZE2oXxNNiu-o2eYovJ_Ia1Dk',
           ],
           'response' => [
               'format' => 'json'
           ],
           'errorHandler' => [
               'errorAction' => 'site/error',
           ],
           'urlManager' => [
               'enablePrettyUrl' => true,
               'showScriptName' => false,
               'rules' => [
               ],
           ],
       ],
   ];
   
   if (YII_ENV_DEV) {
       // configuration adjustments for 'dev' environment
       $config['bootstrap'][] = 'debug';
       $config['modules']['debug'] = [
           'class' => 'yii\debug\Module',
           // uncomment the following to add your IP if you are not connecting from localhost.
           //'allowedIPs' => ['127.0.0.1', '::1'],
       ];
   
       $config['bootstrap'][] = 'gii';
       $config['modules']['gii'] = [
           'class' => 'yii\gii\Module',
           // uncomment the following to add your IP if you are not connecting from localhost.
           //'allowedIPs' => ['127.0.0.1', '::1'],
       ];
   }
   
   return $config;

5. 添加控制器 appcontrollersUserController

   <?php
   
   namespace app\controllers;
   
   use app\services\UserService;
   use yii\base\Module;
   use yii\web\Controller;
   use yii\web\NotFoundHttpException;
   
   class UserController extends Controller
   {
       private $userService;
   
       public function __construct(string $id, Module $module, UserService $userService, array $config = [])
       {
           $this->userService = $userService;
           parent::__construct($id, $module, $config);
       }
   
       public function actionShow($id)
       {
           $user = $this->userService->show($id);
           if (empty($user)) {
               throw new NotFoundHttpException('用戶不存在');
           }
           return $user;
       }
       
       public function actionAll()
       {
           return $this->userService->all();
       }
   }

6. 運行測試服務器

   ./yii serve/index

7. 訪問用戶列表接口 http://localhost:8080/user/all

   [{
       "id": 1,
       "name": "xialei"
   }, {
       "id": 2,
       "name": "zhangsan"
   }]

8. 訪問查看用戶接口 http://localhost:8080/user/show?id=1

   {
       "id": 1,
       "name": "xialei"
   }

寫在最後

如你所見，Yii2自帶的IoC容器使用起來仍是挺方便的，觀測了Yii 配置優於編碼 的思想，Yii的組件基本上均可以在配置文件中進行配置而不須要手動編碼。

靈活使用DI可使咱們從依賴關係中解脫出來，專一於業務邏輯。

固然，業務邏輯的組織也是一個很大的研究課題，有興趣的能夠去看看 DDD(領域驅動設計)