Luman 中 Filesystem 使用如何注册 Factory?

http://lumen.golaravel.com/docs/filesystem...

文档说明:

The Storage facade may be used to interact with any of your configured disks. Alternatively, you may type-hint the Illuminate\Contracts\Filesystem\Factory contract on any class that is resolved via the Laravel service container.

但是看实例,里面写的是new 一个实例出来,但是 Illuminate\Contracts\Filesystem\Factory 是一个接口,接口是没办法实例化的.

可能是我没有正确理解,有人知道怎么做吗?谢谢