$this->app->bind('sender','MailSender');
//$this->app成为服务容器。

$sender = $this->app->make('sender');
//从服务容器（$this->app）创建一个sender类。

$app = new Illuminate\Foundation\Application(
  dirname(__DIR__)
);

$app = app();
//app这个辅助函数定义在\vendor\laravel\framework\src\Illuminate\Foundation\helper.php

Route::get('/', function () {
  dd(App::basePath());
  return '';
});
//这个其实是用到Facade，中文直译貌似叫门面，在config/app.php中，

abstract class ServiceProvider
{
  protected $app;

app()->bind('service', 'this is service1');
app()->bind('service2', [
  'hi' => function(){
    //say hi
  }
]);
class Service {
}
app()->bind('service3', function(){
  return new Service();
});

public function singleton($abstract, $concrete = null)
{
$this->bind($abstract, $concrete, true);
}

if (! $concrete instanceof Closure) {
  $concrete = $this->getClosure($abstract, $concrete);
}

public function bind($abstract, $concrete = null, $shared = false)

app()['service'] = function(){
  return new Service();
};

$service= app()->make('service');

/**
 * Resolve the given type from the container.
 *
 * @param string $abstract
 * @param array $parameters
 * @return mixed
 */
public function make($abstract, array $parameters = [])
{
  return $this->resolve($abstract, $parameters);
}
/**
 * Resolve the given type from the container.
 *
 * @param string $abstract
 * @param array $parameters
 * @return mixed
 */
protected function resolve($abstract, $parameters = [])
{
  $abstract = $this->getAlias($abstract);
  $needsContextualBuild = ! empty($parameters) || ! is_null(
    $this->getContextualConcrete($abstract)
  );
  // If an instance of the type is currently being managed as a singleton we'll
  // just return an existing instance instead of instantiating new instances
  // so the developer can keep using the same objects instance every time.
  if (isset($this->instances[$abstract]) && ! $needsContextualBuild) {
    return $this->instances[$abstract];
  }
  $this->with[] = $parameters;
  $concrete = $this->getConcrete($abstract);
  // We're ready to instantiate an instance of the concrete type registered for
  // the binding. This will instantiate the types, as well as resolve any of
  // its "nested" dependencies recursively until all have gotten resolved.
  if ($this->isBuildable($concrete, $abstract)) {
    $object = $this->build($concrete);
  } else {
    $object = $this->make($concrete);
  }
  // If we defined any extenders for this type, we'll need to spin through them
  // and apply them to the object being built. This allows for the extension
  // of services, such as changing configuration or decorating the object.
  foreach ($this->getExtenders($abstract) as $extender) {
    $object = $extender($object, $this);
  }
  // If the requested type is registered as a singleton we'll want to cache off
  // the instances in "memory" so we can return it later without creating an
  // entirely new instance of an object on each subsequent request for it.
  if ($this->isShared($abstract) && ! $needsContextualBuild) {
    $this->instances[$abstract] = $object;
  }
  $this->fireResolvingCallbacks($abstract, $object);
  // Before returning, we will also set the resolved flag to "true" and pop off
  // the parameter overrides for this build. After those two things are done
  // we will be ready to return back the fully constructed class instance.
  $this->resolved[$abstract] = true;
  array_pop($this->with);
  return $object;
}

$needsContextualBuild = ! empty($parameters) || ! is_null(
  $this->getContextualConcrete($abstract)
);

if (isset($this->instances[$abstract]) && ! $needsContextualBuild) {
  return $this->instances[$abstract];
}

$concrete = $this->getConcrete($abstract);
...
/**
 * Get the concrete type for a given abstract.
 *
 * @param string $abstract
 * @return mixed  $concrete
 */
protected function getConcrete($abstract)
{
  if (! is_null($concrete = $this->getContextualConcrete($abstract))) {
    return $concrete;
  }
  // If we don't have a registered resolver or concrete for the type, we'll just
  // assume each type is a concrete name and will attempt to resolve it as is
  // since the container should be able to resolve concretes automatically.
  if (isset($this->bindings[$abstract])) {
    return $this->bindings[$abstract]['concrete'];
  }
  return $abstract;
}

// We're ready to instantiate an instance of the concrete type registered for
// the binding. This will instantiate the types, as well as resolve any of
// its "nested" dependencies recursively until all have gotten resolved.
if ($this->isBuildable($concrete, $abstract)) {
  $object = $this->build($concrete);
} else {
  $object = $this->make($concrete);
}
...
/**
 * Determine if the given concrete is buildable.
 *
 * @param mixed  $concrete
 * @param string $abstract
 * @return bool
 */
protected function isBuildable($concrete, $abstract)
{
  return $concrete === $abstract || $concrete instanceof Closure;
}

$this->build($concrete)


/**
 * Instantiate a concrete instance of the given type.
 *
 * @param string $concrete
 * @return mixed
 *
 * @throws \Illuminate\Contracts\Container\BindingResolutionException
 */
public function build($concrete)
{
  // If the concrete type is actually a Closure, we will just execute it and
  // hand back the results of the functions, which allows functions to be
  // used as resolvers for more fine-tuned resolution of these objects.
  // 如果传入的是闭包，则直接执行闭包函数，返回结果
  if ($concrete instanceof Closure) {
    return $concrete($this, $this->getLastParameterOverride());
  }
  // 利用反射机制，解析该类。
  $reflector = new ReflectionClass($concrete);
  // If the type is not instantiable, the developer is attempting to resolve
  // an abstract type such as an Interface of Abstract Class and there is
  // no binding registered for the abstractions so we need to bail out.
  if (! $reflector->isInstantiable()) {
    return $this->notInstantiable($concrete);
  }
  $this->buildStack[] = $concrete;
  // 获取构造函数
  $constructor = $reflector->getConstructor();
  // If there are no constructors, that means there are no dependencies then
  // we can just resolve the instances of the objects right away, without
  // resolving any other types or dependencies out of these containers.
  // 如果没有构造函数，则表明没有传入参数，也就意味着不需要做对应的上下文依赖解析。
  if (is_null($constructor)) {
    // 将 build 过程的内容 pop，然后直接构造对象输出。
    array_pop($this->buildStack);
    return new $concrete;
  }
  // 获取构造函数的参数
  $dependencies = $constructor->getParameters();
  // Once we have all the constructor's parameters we can create each of the
  // dependency instances and then use the reflection instances to make a
  // new instance of this class, injecting the created dependencies in.
  // 解析出所有上下文依赖对象，带入函数，构造对象输出
  $instances = $this->resolveDependencies(
    $dependencies
  );
  array_pop($this->buildStack);
  return $reflector->newInstanceArgs($instances);
}