Read Laravel and see how PHP implements facade?

Just beginning to learn Laravel will come into contact with routing

123	Route::get(‘/‘, function() {    returnview(‘welcome‘);});

Later I seriously read the code of the Route class, surprised to find that there is no get this method, then learned that Laravel used the facade mode.

Facade is essentially a class that "pushes work to others."

The value of facade existence can be discussed from the service container. Service container, see my other blog post, address: http://www.cnblogs.com/sweng/p/6430374.html

For example, I do not know if you have ever written code before Obj->method (ARG1,ARG2)->func (ARG3,ARG4), the experience. The reader of the service container knows that this line of code is to take out the object in the service container and invoke his method. This code is acceptable to developers who are familiar with which classes are registered in the service container. But it's too much of an elegant way to write a lengthy form like a route definition. So using facade mode can be a good way to simplify the code length.

Let's write a DB class first.

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namespaceAPI;classDB{    publicfunction__construct($args){    }    publicfunctionWrite($str){        echo‘Write:‘.$str.PHP_EOL;    }    publicfunctionRead($str){        echo‘Read:‘.$str.PHP_EOL;    }}

Database read and write is a very common operation of the whole system. But DB class is registered in the service container, every time the database read and write to the DB Class object from the service container, it is very inconvenient.

We write a facade class

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classFacade{    publicfunction__construct(){        //    }        publicstaticfunctiongetInstance($classname,$args){        returnnew$classname($args);    }        publicstaticfunctiongetFacadeAccessor(){        //    }        publicstaticfunction__callstatic($method,$arg){        $instance=static::getInstance(static::getFacadeAccessor(),[1,2,3]);        returncall_user_func_array(array($instance,$method),$arg);    }}

To understand this class, we just focus on the last function, the __callstatic magic method. This method is called the __callstatic method, which is the role of a "candidate" when the facade type object calls a function that he has not defined himself.

We'll define a Dbfacade class.

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classDBFacade extends Facade{    public static function getFacadeAccessor(){        returnAPI\DB::class;    }}

Each facade subclass implements the Getfacadeaccessor method, which returns just a string of class names used to substitute the GetInstance method to create a truly "do-it-yourself" class.

At this point, facade is ready for use, and we call the static method of Dbfacade

1	DBFacade::Write(‘hello‘);

Reading the code, we found that, in fact, Dbfacade is not the Write method, and then call his father class facade __callstatic Magic method, Magic method we have in the parent class has been implemented.

Previously heard peer complaints, PHP grammar chaos, difficult to remember. But in fact, like the magic method of facade implementation of the very concise, visible syntax design subtle.

Read Laravel and see how PHP implements facade?