如何使用Laravel Eloquent来开发无限极分类

Schema::create('categories', function (Blueprint $table) {
 $table->bigIncrements('id');
 $table->string('name');
 $table->unsignedBigInteger('category_id')->nullable();
 $table->foreign('category_id')->references('id')->on('categories');
 $table->timestamps();
});

class Category extends Model
{
 public function categories()
 {
 return $this->hasMany(Category::class);
 }
}

public function childrenCategories()
{
 return $this->hasMany(Category::class)->with('categories');
}

Route::get('categories', 'CategoryController@index');

public function index()
{
 $categories = Category::whereNull('category_id')
 ->with('childrenCategories')
 ->get();
 return view('categories', compact('categories'));
}

<ul>
 @foreach ($categories as $category)
 <li>{{ $category->name }}</li>
 <ul>
 @foreach ($category->childrenCategories as $childCategory)
 @include('child_category', ['child_category' => $childCategory])
 @endforeach
 </ul>
 @endforeach
</ul>

<li>{{ $child_category->name }}</li>
@if ($child_category->categories)
 <ul>
 @foreach ($child_category->categories as $childCategory)
 @include('child_category', ['child_category' => $childCategory])
 @endforeach
 </ul>
@endif