Laravel之Contracts和Facades

摘要：而这些通用的接口已经由为你设计好了。作为在服务容器内基类的静态代理。所有对的调用都会被转发到该类对象下。在注册类在注册自定义的别名使用测试去查看输出

Contracts其实就是倡导面向接口编程，来达到解耦的目的。而这些通用的接口已经由Laravel为你设计好了。就是这些Contracts.
那么Laravel如何知道我们需要使用哪个实现呢？
在Laravel默认的Contracts绑定中，在"Illuminate/Foundation/Application.php"有这样的定义:这就是绑定了默认的接口实现.

  /**
     * Register the core class aliases in the container.
     *
     * @return void
     */
    public function registerCoreContainerAliases()
    {
        $aliases = [
            "app"                  => ["IlluminateFoundationApplication", "IlluminateContractsContainerContainer", "IlluminateContractsFoundationApplication"],
            "auth"                 => "IlluminateAuthAuthManager",
            "auth.driver"          => ["IlluminateAuthGuard", "IlluminateContractsAuthGuard"],
            "auth.password.tokens" => "IlluminateAuthPasswordsTokenRepositoryInterface",
            "blade.compiler"       => "IlluminateViewCompilersBladeCompiler",
            "cache"                => ["IlluminateCacheCacheManager", "IlluminateContractsCacheFactory"],
            "cache.store"          => ["IlluminateCacheRepository", "IlluminateContractsCacheRepository"],
            "config"               => ["IlluminateConfigRepository", "IlluminateContractsConfigRepository"],
            "cookie"               => ["IlluminateCookieCookieJar", "IlluminateContractsCookieFactory", "IlluminateContractsCookieQueueingFactory"],
            "encrypter"            => ["IlluminateEncryptionEncrypter", "IlluminateContractsEncryptionEncrypter"],
            "db"                   => "IlluminateDatabaseDatabaseManager",
            "db.connection"        => ["IlluminateDatabaseConnection", "IlluminateDatabaseConnectionInterface"],
            "events"               => ["IlluminateEventsDispatcher", "IlluminateContractsEventsDispatcher"],
            "files"                => "IlluminateFilesystemFilesystem",
            "filesystem"           => ["IlluminateFilesystemFilesystemManager", "IlluminateContractsFilesystemFactory"],
            "filesystem.disk"      => "IlluminateContractsFilesystemFilesystem",
            "filesystem.cloud"     => "IlluminateContractsFilesystemCloud",
            "hash"                 => "IlluminateContractsHashingHasher",
            "translator"           => ["IlluminateTranslationTranslator", "SymfonyComponentTranslationTranslatorInterface"],
            "log"                  => ["IlluminateLogWriter", "IlluminateContractsLoggingLog", "PsrLogLoggerInterface"],
            "mailer"               => ["IlluminateMailMailer", "IlluminateContractsMailMailer", "IlluminateContractsMailMailQueue"],
            "auth.password"        => ["IlluminateAuthPasswordsPasswordBroker", "IlluminateContractsAuthPasswordBroker"],
            "queue"                => ["IlluminateQueueQueueManager", "IlluminateContractsQueueFactory", "IlluminateContractsQueueMonitor"],
            "queue.connection"     => "IlluminateContractsQueueQueue",
            "redirect"             => "IlluminateRoutingRedirector",
            "redis"                => ["IlluminateRedisDatabase", "IlluminateContractsRedisDatabase"],
            "request"              => "IlluminateHttpRequest",
            "router"               => ["IlluminateRoutingRouter", "IlluminateContractsRoutingRegistrar"],
            "session"              => "IlluminateSessionSessionManager",
            "session.store"        => ["IlluminateSessionStore", "SymfonyComponentHttpFoundationSessionSessionInterface"],
            "url"                  => ["IlluminateRoutingUrlGenerator", "IlluminateContractsRoutingUrlGenerator"],
            "validator"            => ["IlluminateValidationFactory", "IlluminateContractsValidationFactory"],
            "view"                 => ["IlluminateViewFactory", "IlluminateContractsViewFactory"],
        ];

在我们自定义的接口实现时，我们可以在ServiceProvider中使用进行绑定:

$this->app->bind("AppContractsEventPusher", "AppServicesPusherEventPusher");

Facades 为应用程序的服务容器中可用的类提供了一个「静态」接口。Laravel 「facades」作为在服务容器内基类的「静态代理」。很难懂？
我们打开项目目录下的config/app.php，然后找到

/*
    |--------------------------------------------------------------------------
    | 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"       => IlluminateSupportFacadesApp::class,
        "Artisan"   => IlluminateSupportFacadesArtisan::class,
        "Auth"      => IlluminateSupportFacadesAuth::class,
        "Blade"     => IlluminateSupportFacadesBlade::class,
        "Bus"       => IlluminateSupportFacadesBus::class,
        "Cache"     => IlluminateSupportFacadesCache::class,
        "Config"    => IlluminateSupportFacadesConfig::class,
        "Cookie"    => IlluminateSupportFacadesCookie::class,
        "Crypt"     => IlluminateSupportFacadesCrypt::class,
        "DB"        => IlluminateSupportFacadesDB::class,
        "Eloquent"  => IlluminateDatabaseEloquentModel::class,
        "Event"     => IlluminateSupportFacadesEvent::class,
        "File"      => IlluminateSupportFacadesFile::class,
        "Gate"      => IlluminateSupportFacadesGate::class,
        "Hash"      => IlluminateSupportFacadesHash::class,
        "Input"     => IlluminateSupportFacadesInput::class,
        "Lang"      => IlluminateSupportFacadesLang::class,
        "Log"       => IlluminateSupportFacadesLog::class,
        "Mail"      => IlluminateSupportFacadesMail::class,
        "Password"  => IlluminateSupportFacadesPassword::class,
        "Queue"     => IlluminateSupportFacadesQueue::class,
        "Redirect"  => IlluminateSupportFacadesRedirect::class,
        "Redis"     => IlluminateSupportFacadesRedis::class,
        "Request"   => IlluminateSupportFacadesRequest::class,
        "Response"  => IlluminateSupportFacadesResponse::class,
        "Route"     => IlluminateSupportFacadesRoute::class,
        "Schema"    => IlluminateSupportFacadesSchema::class,
        "Session"   => IlluminateSupportFacadesSession::class,
        "Storage"   => IlluminateSupportFacadesStorage::class,
        "URL"       => IlluminateSupportFacadesURL::class,
        "Validator" => IlluminateSupportFacadesValidator::class,
        "View"      => IlluminateSupportFacadesView::class,

    ],

你是不是发现了什么？对，Facades其实就是在config/app.php中定义的一系列类的别名。只不过这些类都具有一个共同的特点，那就是继承基底 IlluminateSupportFacadesFacade 类并实现一个方法：getFacadeAccessor返回名称。

参考http://www.tutorialspoint.com/laravel/laravel_facades.htm
Step 1 −创建一个名为 TestFacadesServiceProvider的ServiceProvider ,使用如下命令即可:

php artisan make:provider TestFacadesServiceProvider

Step 2 − 创建一个底层代理类，命名为“TestFacades.php” at “App/Test”.
App/Test/TestFacades.php

Step 3 − 创建一个 Facade 类 called “TestFacades.php” at “App/Test/Facades”.
App/Test/Facades/TestFacades.php

Step 4 −创建一个ServiceProviders类，名为“TestFacadesServiceProviders.php” at “App/Test/Facades”.
App/Providers/TestFacadesServiceProviders.php
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.php注册ServiceProvider类
Step 6 − 在config/app.php注册自定义Facade的别名
使用测试：
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去查看输出