Laravel之Contracts和Facades詳解

Contracts

Contracts其實就是倡導面向介面編程，來達到解耦的目的。而這些通用的介面已經由Laravel為你設計好了。就是這些Contracts.

那麼Laravel如何知道我們需要使用哪個實現呢？

在Laravel預設的Contracts綁定中，在'Illuminate/Foundation/Application.php'有這樣的定義:這就是綁定了預設的介面實現.

/**

     * Register the core class aliases in the container.

     *

     * @return void

     */

    public function registerCoreContainerAliases()

    {

        $aliases = [

            'app'                  => ['Illuminate\Foundation\Application', 'Illuminate\Contracts\Container\Container', 'Illuminate\Contracts\Foundation\Application'],

            'auth'                 => 'Illuminate\Auth\AuthManager',

            'auth.driver'          => ['Illuminate\Auth\Guard', 'Illuminate\Contracts\Auth\Guard'],

            'auth.password.tokens' => 'Illuminate\Auth\Passwords\TokenRepositoryInterface',

            'blade.compiler'       => 'Illuminate\View\Compilers\BladeCompiler',

            'cache'                => ['Illuminate\Cache\CacheManager', 'Illuminate\Contracts\Cache\Factory'],

            'cache.store'          => ['Illuminate\Cache\Repository', 'Illuminate\Contracts\Cache\Repository'],

            'config'               => ['Illuminate\Config\Repository', 'Illuminate\Contracts\Config\Repository'],

            'cookie'               => ['Illuminate\Cookie\CookieJar', 'Illuminate\Contracts\Cookie\Factory', 'Illuminate\Contracts\Cookie\QueueingFactory'],

            'encrypter'            => ['Illuminate\Encryption\Encrypter', 'Illuminate\Contracts\Encryption\Encrypter'],

            'db'                   => 'Illuminate\Database\DatabaseManager',

            'db.connection'        => ['Illuminate\Database\Connection', 'Illuminate\Database\ConnectionInterface'],

            'events'               => ['Illuminate\Events\Dispatcher', 'Illuminate\Contracts\Events\Dispatcher'],

            'files'                => 'Illuminate\Filesystem\Filesystem',

            'filesystem'           => ['Illuminate\Filesystem\FilesystemManager', 'Illuminate\Contracts\Filesystem\Factory'],

            'filesystem.disk'      => 'Illuminate\Contracts\Filesystem\Filesystem',

            'filesystem.cloud'     => 'Illuminate\Contracts\Filesystem\Cloud',

            'hash'                 => 'Illuminate\Contracts\Hashing\Hasher',

            'translator'           => ['Illuminate\Translation\Translator', 'Symfony\Component\Translation\TranslatorInterface'],

            'log'                  => ['Illuminate\Log\Writer', 'Illuminate\Contracts\Logging\Log', 'Psr\Log\LoggerInterface'],

            'mailer'               => ['Illuminate\Mail\Mailer', 'Illuminate\Contracts\Mail\Mailer', 'Illuminate\Contracts\Mail\MailQueue'],

            'auth.password'        => ['Illuminate\Auth\Passwords\PasswordBroker', 'Illuminate\Contracts\Auth\PasswordBroker'],

            'queue'                => ['Illuminate\Queue\QueueManager', 'Illuminate\Contracts\Queue\Factory', 'Illuminate\Contracts\Queue\Monitor'],

            'queue.connection'     => 'Illuminate\Contracts\Queue\Queue',

            'redirect'             => 'Illuminate\Routing\Redirector',

            'redis'                => ['Illuminate\Redis\Database', 'Illuminate\Contracts\Redis\Database'],

            'request'              => 'Illuminate\Http\Request',

            'router'               => ['Illuminate\Routing\Router', 'Illuminate\Contracts\Routing\Registrar'],

            'session'              => 'Illuminate\Session\SessionManager',

            'session.store'        => ['Illuminate\Session\Store', 'Symfony\Component\HttpFoundation\Session\SessionInterface'],

            'url'                  => ['Illuminate\Routing\UrlGenerator', 'Illuminate\Contracts\Routing\UrlGenerator'],

            'validator'            => ['Illuminate\Validation\Factory', 'Illuminate\Contracts\Validation\Factory'],

            'view'                 => ['Illuminate\View\Factory', 'Illuminate\Contracts\View\Factory'],

        ];

在我們自定義的介面實現時，我們可以在ServiceProvider中使用進行綁定:

$this->app->bind('App\Contracts\EventPusher', 'App\Services\PusherEventPusher');

Facades

Facades 為應用程式的服務容器中可用的類提供了一個「靜態」介面。Laravel 「facades」作為在服務容器內基類的「靜態代理」。很難懂？

我們打開項目目錄下的config/app.php，然後找到

/*

    |--------------------------------------------------------------------------

    | Class Aliases

    |--------------------------------------------------------------------------

    |

    | This array of class aliases will be registered when this application

    | is started. However, feel free to register as many as you wish as

    | the aliases are "lazy" loaded so they don't hinder performance.

    |

    */

    'aliases' => [

        'App'       => Illuminate\Support\Facades\App::class,

        'Artisan'   => Illuminate\Support\Facades\Artisan::class,

        'Auth'      => Illuminate\Support\Facades\Auth::class,

        'Blade'     => Illuminate\Support\Facades\Blade::class,

        'Bus'       => Illuminate\Support\Facades\Bus::class,

        'Cache'     => Illuminate\Support\Facades\Cache::class,

        'Config'    => Illuminate\Support\Facades\Config::class,

        'Cookie'    => Illuminate\Support\Facades\Cookie::class,

        'Crypt'     => Illuminate\Support\Facades\Crypt::class,

        'DB'        => Illuminate\Support\Facades\DB::class,

        'Eloquent'  => Illuminate\Database\Eloquent\Model::class,

        'Event'     => Illuminate\Support\Facades\Event::class,

        'File'      => Illuminate\Support\Facades\File::class,

        'Gate'      => Illuminate\Support\Facades\Gate::class,

        'Hash'      => Illuminate\Support\Facades\Hash::class,

        'Input'     => Illuminate\Support\Facades\Input::class,

        'Lang'      => Illuminate\Support\Facades\Lang::class,

        'Log'       => Illuminate\Support\Facades\Log::class,

        'Mail'      => Illuminate\Support\Facades\Mail::class,

        'Password'  => Illuminate\Support\Facades\Password::class,

        'Queue'     => Illuminate\Support\Facades\Queue::class,

        'Redirect'  => Illuminate\Support\Facades\Redirect::class,

        'Redis'     => Illuminate\Support\Facades\Redis::class,

        'Request'   => Illuminate\Support\Facades\Request::class,

        'Response'  => Illuminate\Support\Facades\Response::class,

        'Route'     => Illuminate\Support\Facades\Route::class,

        'Schema'    => Illuminate\Support\Facades\Schema::class,

        'Session'   => Illuminate\Support\Facades\Session::class,

        'Storage'   => Illuminate\Support\Facades\Storage::class,

        'URL'       => Illuminate\Support\Facades\URL::class,

        'Validator' => Illuminate\Support\Facades\Validator::class,

        'View'      => Illuminate\Support\Facades\View::class,

    ],

你是不是發現了什麼？對，Facades其實就是在config/app.php中定義的一系列類的別名。只不過這些類都具有一個共同的特點，那就是繼承基底 Illuminate\Support\Facades\Facade 類並實現一個方法：getFacadeAccessor返回名稱。

自定義Facade

參考http://www.tutorialspoint.com/laravel/laravel_facades.htm

Step 1 −創建一個名為 TestFacadesServiceProvider的ServiceProvider ,使用如下命令即可:

php artisan make:provider TestFacadesServiceProvider

Step 2 − 創建一個底層代理類，命名為“TestFacades.php” at “App/Test”.

App/Test/TestFacades.php

<?php

namespace App\Test;

class TestFacades{

   public function testingFacades(){

      echo "Testing the Facades in Laravel.";

   }

}

?>

Step 3 − 創建一個 Facade 類 called “TestFacades.php” at “App/Test/Facades”.

App/Test/Facades/TestFacades.php

<?php

namespace app\Test\Facades;

use Illuminate\Support\Facades\Facade;

class TestFacades extends Facade{

   protected static function getFacadeAccessor() { return 'test'; }

}

Step 4 −創建一個ServiceProviders類，名為“TestFacadesServiceProviders.php” at “App/Test/Facades”.

App/Providers/TestFacadesServiceProviders.php

<?php
namespace App\Providers;
use App;
use Illuminate\Support\ServiceProvider;
class TestFacadesServiceProvider extends ServiceProvider {
 public function boot() {
 //
 }
 public function register() {
 //可以這麼綁定,這需要use App;
 //  App::bind('test',function() {
 //     return new \App\Test\TestFacades;
 //  });
  
 //也可以這麼綁定，推薦。這個test對應於Facade的getFacadeAccessor返回值
 $this->app->bind("test", function(){
 return new MyFoo(); //給這個Facade返回一個代理實例。所有對Facade的調用都會被轉發到該類對象下。
 });
 }
}

Step 5 − 在config/app.php註冊ServiceProvider類

Step 6 − 在config/app.php註冊自定義Facade的別名

使用測試：

Add the following lines in app/Http/routes.php.

Route::get('/facadeex', function(){
 return TestFacades::testingFacades();
});

Step 9 − Visit the following URL to test the Facade.

http://localhost:8000/facadeex去查看輸出

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