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作呢？

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作.

#推薦：《laravel教學》

/**
     * 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'],
        ];

在我們自訂的介面實作時，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別提供了一個「靜態」介面。 Laravel “facades”作為在服務容器內基類的「靜態代理」。很難懂？

我們開啟專案目錄下的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中定義的一系列類別的別名。只不過這些類別都有一個共同的特點，那就是繼承基底 Illuminate\Support\Facades\Facade 類別並實作一個方法：getFacadeAccessor傳回名稱。

自訂Facade

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

Step 1 −建立一個名為TestFacadesServiceProvider的ServiceProvider ,使用以下命令即可:

php artisan make:provider TestFacadesServiceProvider

#Step 2 − 建立一個底層代理類，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 − 建立一個Facade 類別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 &#39;test&#39;; }
}

Step 4 −建立一個ServiceProviders類，名稱為「 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() {
     //可以这么绑定,这需要use App;
    //  App::bind(&#39;test&#39;,function() {
    //     return new \App\Test\TestFacades;
    //  });
     
     //也可以这么绑定，推荐。这个test对应于Facade的getFacadeAccessor返回值
        $this->app->bind("test", function(){
            return new MyFoo(); //给这个Facade返回一个代理实例。所有对Facade的调用都会被转发到该类对象下。
        });
   }
}

Step 5 − 在config/app.phpServiceProviderer類別

Step 6 − 在config/app.php註冊自訂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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