what is laravel facade

In laravel, the facade is a "static" interface provided for the binding class in the application service container. It can provide easier to test, more flexible, concise and elegant syntax during maintenance. All facades are defined in the "Illuminate\Support\Facades" namespace.

#The operating environment of this article: Windows 10 system, Laravel version 6, Dell G3 computer.

What is laravel facade

Facades provides a "static" interface for binding classes in the application service container.

Laravel has many built-in Facades, which can access most of Laravel's functions.

Laravel's facade serves as a "static proxy" for the underlying class in the service container. Compared with traditional static methods, it can provide easier to test, more flexible, concise and elegant syntax during maintenance.

All Laravel facades are defined under the Illuminate\Support\Facades namespace.

We can easily access the facade:

use Illuminate\Support\Facades\Cache;
Route::get('/cache', function () {
    return Cache::get('key');
});

Throughout the Laravel documentation, many examples use the facade to demonstrate the various functional features of the framework.

When to use Facades

Facades have many advantages. They provide a simple and easy-to-remember syntax, allowing us to use them without having to remember long class names. The functional features provided by Laravel, in addition, make them easy to test due to their unique use of PHP dynamic methods.

When using Facades, there are some places that require special attention.

The main risk of using Facades is that it will cause the scope of the class to expand.

Because Facades are very simple to use and do not require injection, we will inadvertently use many Facades in a single class, causing the class to become larger and larger.

When using dependency injection, the more classes used, the longer the constructor will be, which will attract visual attention and remind you that this class is a bit huge. Therefore, when using Facades, pay special attention to controlling the size of the class to keep the scope of the class short.

When developing third-party extension packages that interact with Laravel, it is recommended to inject the Laravel contract instead of using Facades to use classes. Because extensions are built outside of Laravel itself, you cannot use Laravel Facades to test helper functions.

Facades Vs. Dependency Injection

One of the main advantages of dependency injection is the ability to switch the implementation of the injected class. This is useful when testing because you can inject a mock or stub and assert various methods called on the stub.

Usually, truly static methods cannot be mocked or stubbed. However, because Facades use dynamic methods to proxy method calls on objects resolved from the service container, we can test Facades just like we test injected class instances. For example, like the following route:

use Illuminate\Support\Facades\Cache;
 
Route::get('/cache', function () {
    return Cache::get('key');
})

We can write a test like this to verify that the Cache::get method is called in the way we expect:

use Illuminate\Support\Facades\Cache;
/**
 * 一个基础功能的测试用例。
 *
 * @return void
 */
public function testBasicExample()
{
Cache::shouldReceive('get')
->with('key')
->andReturn('value');
$this->visit('/cache')
->see('value');
}

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