15. Laravel 神奇的 Manager 类

[Bruce Lam]

Laravel 有不少门面类，如 Session、View 初一看令人诈舌，这些类的功能类不只一个，那么 Laravel 是怎么让这些奇葩的门面通往不止一个后门的？

类声明

laravel/vendor/laravel/framework/src/Illuminate/Support/Manager.php

Lines 3 to 9 in ca57c28

 namespace Illuminate\Support; 
  
 use Closure; 
 use InvalidArgumentException; 
  
 abstract class Manager 
 { 

这是一个抽象类。

属性

laravel/vendor/laravel/framework/src/Illuminate/Support/Manager.php

Lines 10 to 29 in ca57c28

     /** 
      * The application instance. 
      * 
      * @var \Illuminate\Foundation\Application 
      */ 
     protected $app; 
  
     /** 
      * The registered custom driver creators. 
      * 
      * @var array 
      */ 
     protected $customCreators = []; 
  
     /** 
      * The array of created "drivers". 
      * 
      * @var array 
      */ 
     protected $drivers = []; 

$app 是容器，这个 $customCreators 是什么鬼没看懂我们可以不管它。后面这个 $drivers，是一个数组，放的什么东西呢？

driver 在英语中是驱动器的意思。

算了。。。再这么讲下去太拖了。我们拉到最后

魔术函数

laravel/vendor/laravel/framework/src/Illuminate/Support/Manager.php

Lines 144 to 147 in ca57c28

 public function __call($method, $parameters) 
 { 
     return $this->driver()->$method(...$parameters); 
 } 

我们看到，当调用到当前实现类不存在方法时会调用 $this->driver() 下的同名方法。

laravel/vendor/laravel/framework/src/Illuminate/Support/Manager.php

Lines 57 to 75 in ca57c28

 public function driver($driver = null) 
 { 
     $driver = $driver ?: $this->getDefaultDriver(); 
  
     if (is_null($driver)) { 
         throw new InvalidArgumentException(sprintf( 
             'Unable to resolve NULL driver for [%s].', static::class 
         )); 
     } 
  
     // If the given driver has not been created before, we will create the instances 
     // here and cache it so we can return it next time very quickly. If there is 
     // already a driver created by this name, we'll just return that instance. 
     if (! isset($this->drivers[$driver])) { 
         $this->drivers[$driver] = $this->createDriver($driver); 
     } 
  
     return $this->drivers[$driver]; 
 } 

然后 getDefaultDriver，

laravel/vendor/laravel/framework/src/Illuminate/Support/Manager.php

Line 47 in ca57c28

 abstract public function getDefaultDriver(); 

这是抽象函数，我们到具体的例子中看吧。比如 session

laravel/vendor/laravel/framework/src/Illuminate/Session/SessionManager.php

Lines 200 to 203 in ca57c28

 public function getDefaultDriver() 
 { 
     return $this->app['config']['session.driver']; 
 } 

---

所以，这些继承于 Illuminate\Support\Manager 的门后类，实现了向 driver 的穿透。

总结： Manager first, driver end. 经理先行，司机垫后