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Laravel中对一些概念的简单理解(服务提供者/IOC容器等)

Laravel中对一些概念的简单理解(服务提供者/IOC容器等)

作者: 曹轩跃 | 来源:发表于2017-03-22 16:09 被阅读0次

    说明:只是笔者自身对这些概念的理解,不妥之处欢迎纠正。

    1、什么叫做服务(Service)?

    服务其实就是一个组件,再通俗点讲,composer里的一个package就是一个服务,有的地方把服务称之为bundle,或者Componet。

    config/app.php
    

    app.php内容:

    return [
    
        /*
        |--------------------------------------------------------------------------
        | Application Name
        |--------------------------------------------------------------------------
        |
        | This value is the name of your application. This value is used when the
        | framework needs to place the application's name in a notification or
        | any other location as required by the application or its packages.
        */
    
        'name' => 'Laravel',
    
        /*
        |--------------------------------------------------------------------------
        | Application Environment
        |--------------------------------------------------------------------------
        |
        | This value determines the "environment" your application is currently
        | running in. This may determine how you prefer to configure various
        | services your application utilizes. Set this in your ".env" file.
        |
        */
    
        'env' => env('APP_ENV', 'production'),
    
        /*
        |--------------------------------------------------------------------------
        | Application Debug Mode
        |--------------------------------------------------------------------------
        |
        | When your application is in debug mode, detailed error messages with
        | stack traces will be shown on every error that occurs within your
        | application. If disabled, a simple generic error page is shown.
        |
        */
    
        'debug' => env('APP_DEBUG', false),
    
        /*
        |--------------------------------------------------------------------------
        | Application URL
        |--------------------------------------------------------------------------
        |
        | This URL is used by the console to properly generate URLs when using
        | the Artisan command line tool. You should set this to the root of
        | your application so that it is used when running Artisan tasks.
        |
        */
    
        'url' => env('APP_URL', 'http://localhost'),
    
        /*
        |--------------------------------------------------------------------------
        | Application Timezone
        |--------------------------------------------------------------------------
        |
        | Here you may specify the default timezone for your application, which
        | will be used by the PHP date and date-time functions. We have gone
        | ahead and set this to a sensible default for you out of the box.
        |
        */
    
        'timezone' => 'UTC',
    
        /*
        |--------------------------------------------------------------------------
        | Application Locale Configuration
        |--------------------------------------------------------------------------
        |
        | The application locale determines the default locale that will be used
        | by the translation service provider. You are free to set this value
        | to any of the locales which will be supported by the application.
        |
        */
    
        'locale' => 'en',
    
        /*
        |--------------------------------------------------------------------------
        | Application Fallback Locale
        |--------------------------------------------------------------------------
        |
        | The fallback locale determines the locale to use when the current one
        | is not available. You may change the value to correspond to any of
        | the language folders that are provided through your application.
        |
        */
    
        'fallback_locale' => 'en',
    
        /*
        |--------------------------------------------------------------------------
        | Encryption Key
        |--------------------------------------------------------------------------
        |
        | This key is used by the Illuminate encrypter service and should be set
        | to a random, 32 character string, otherwise these encrypted strings
        | will not be safe. Please do this before deploying an application!
        |
        */
    
        'key' => env('APP_KEY'),
    
        'cipher' => 'AES-256-CBC',
    
        /*
        |--------------------------------------------------------------------------
        | Logging Configuration
        |--------------------------------------------------------------------------
        |
        | Here you may configure the log settings for your application. Out of
        | the box, Laravel uses the Monolog PHP logging library. This gives
        | you a variety of powerful log handlers / formatters to utilize.
        |
        | Available Settings: "single", "daily", "syslog", "errorlog"
        |
        */
    
        'log' => env('APP_LOG', 'single'),
    
        'log_level' => env('APP_LOG_LEVEL', 'debug'),
    
        /*
        |--------------------------------------------------------------------------
        | Autoloaded Service Providers
        |--------------------------------------------------------------------------
        |
        | The service providers listed here will be automatically loaded on the
        | request to your application. Feel free to add your own services to
        | this array to grant expanded functionality to your applications.
        |
        */
    
        'providers' => [
    
            /*
             * Laravel Framework Service Providers...
             */
            Illuminate\Auth\AuthServiceProvider::class,
            Illuminate\Broadcasting\BroadcastServiceProvider::class,
            Illuminate\Bus\BusServiceProvider::class,
            Illuminate\Cache\CacheServiceProvider::class,
            Illuminate\Foundation\Providers\ConsoleSupportServiceProvider::class,
            Illuminate\Cookie\CookieServiceProvider::class,
            Illuminate\Database\DatabaseServiceProvider::class,
            Illuminate\Encryption\EncryptionServiceProvider::class,
            Illuminate\Filesystem\FilesystemServiceProvider::class,
            Illuminate\Foundation\Providers\FoundationServiceProvider::class,
            Illuminate\Hashing\HashServiceProvider::class,
            Illuminate\Mail\MailServiceProvider::class,
            Illuminate\Notifications\NotificationServiceProvider::class,
            Illuminate\Pagination\PaginationServiceProvider::class,
            Illuminate\Pipeline\PipelineServiceProvider::class,
            Illuminate\Queue\QueueServiceProvider::class,
            Illuminate\Redis\RedisServiceProvider::class,
            Illuminate\Auth\Passwords\PasswordResetServiceProvider::class,
            Illuminate\Session\SessionServiceProvider::class,
            Illuminate\Translation\TranslationServiceProvider::class,
            Illuminate\Validation\ValidationServiceProvider::class,
            Illuminate\View\ViewServiceProvider::class,
    
            /*
             * Package Service Providers...
             */
    
            //
    
            /*
             * Application Service Providers...
             */
            App\Providers\AppServiceProvider::class,
            App\Providers\AuthServiceProvider::class,
            // App\Providers\BroadcastServiceProvider::class,
            App\Providers\EventServiceProvider::class,
            App\Providers\RouteServiceProvider::class,
    
        ],
    
        /*
        |--------------------------------------------------------------------------
        | 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,
            'Lang' => Illuminate\Support\Facades\Lang::class,
            'Log' => Illuminate\Support\Facades\Log::class,
            'Mail' => Illuminate\Support\Facades\Mail::class,
            'Notification' => Illuminate\Support\Facades\Notification::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,
    
        ],
    
    ];
    

    这个文件是laravel框架组重要的文件之一,composer的包使用前都要在这里绑定一下,也就是说服务需要在这里绑定一下才会被启动加载到。

    2、什么叫服务提供者(Service Providers)?

    服务不仅要加载,而且还要先注册一下才能被使用,什么叫注册呢?其实就是一个外部服务(包)和Laravel核心程序的连接行为,这个连接器就叫做服务提供者(Service Provider)。

    他的位置位于:

    app/Providers
    

    Service Provider 里面一般有两个重要的方法:boot()和register();

    • 前者是用来启动前期加载一些程序逻辑。
    • 后者则是用来注册外部的服务。

    注意:boot()非常常用,请记住,Service Providers 和 Service Container 有密度关系,下面会讲。

    3、什么叫做依赖注入?

    大多数面向对象的编程语言,在调用一个类的时候,先要实例化这个类,生成一个对象。

    如果你在写一个类,过程中要调用到很多类,甚至这里的“其他类”也要“依赖”于更多的其他类,那么可以想象,你要进行多少次实例化。这就是“依赖“的意思。

    依赖注入,全称是”依赖注入到容器“,容器(IOC容器)是一个设计模式,他也是个对象,你把某个类(不管有多少个依赖关系)放入到这个容器中,可以”解析“出这个类的实例。所以”依赖注入“就是把所有有依赖关系(或者没有)的类放入容器(IOC)容器中,然后解析出这个类的实例,仅此而已。

    4、什么叫做IOC容器?

    容器是个对象,Laravel有一个核心类,叫做application,程序启动的时候就实例化了这个类,放到$app,这个类就是IOC容器。

    注意:转载请标明出处,并以链接方式标出,否则后果自负。

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