laravel中的Contracts, ServiceContainer, ServiceProvider, Facades关系

namespace App\Helper;
class MyFoo
{
    public function add($a, $b)
    {
        return $a+$b;
    }
}

<?php
namespace App\Providers;

use App\Helper\MyFoo; //要服务的Container
use Illuminate\Support\ServiceProvider;
use App;

class MyFooServiceProvider extends ServiceProvider
{
    public function boot(){}
    //注册到容器中
    public function register()
    {
        //可以这么绑定,这需要use App;
        App::bind("myfoo",function(){
            return new MyFoo();
        });
        //也可以这么绑定
        $this->app->bind("myfoo", function(){
            return new MyFoo();
        });
    }
}

App\Providers\MyFooServiceProvider::class,

public function two($id=null)
{
    //从系统容器中获取实例化对象
    $myfoo = App::make("myfoo");
    echo $myfoo->add(1,2);
}

namespace App\Facades;
use Illuminate\Support\Facades\Facade;

class MyFooFacade extends Facade
{
    protected static function getFacadeAccessor()
    {
        //这里返回的是ServiceProvider中注册时,定义的字符串
        return ‘myfoo‘;
    }
}