public function edit($id, Category $category)
    {
        $product = Product::where('id',$id)->first();
        $categories = Category::whereNull('category_id')->with('childrenCategories')->get();
        return view('product.edit', compact('categories','product'));

    }


ErrorException
Undefined variable: category (View: /var/www/bossphp.x/resources/views/product/edit.blade.php)
http://bossphp.x:8080/product/edit/38


<div class="form-group">
            <label>Подкатегории</label>
            <select  class="form-control input-sm" name="category_id">
                <!--                --><?php //dd($categories); ?>
                <option selected value="{{$product->category_id}}">--select--</option>
                @foreach ($categories as $firstcategory)
                    <option @if($firstcategory->id == $category->category_id) selected @endif value="{{$firstcategory->id}}">{{$firstcategory->title}}</option>

                    @if($firstcategory->categories)
                        @foreach ($firstcategory->categories as $subcategory)
                            <option @if($subcategory->id == $category->category_id) selected @endif  value="{{$subcategory->id}}">-----{{$subcategory->title}}</option>
                        @endforeach
                    @endif
                @endforeach
            </select>
        </div>