Php 在laravel 5.3中编辑产品时，类别和子类别不可提取

我试图更新我的产品，但为此，我必须从数据库中获取所有数据，一切正常，除了类别和子类别，它没有显示在选择框中

这是我的刀片文件代码

                <div class="form-group">
                    <label>Brand</label>
                    <select class="form-control" name="brand_id" id="brand_id">
                        <option value=""></option>
                        @foreach($brands as $brand)
                            <option value="{{ $brand->id }}" {{ $product->brand_id == $brand->id ? "selected" : "" }}>{{ $brand->brand_name }}</option>
                        @endforeach
                    </select>

                </div>


              <div class="form-group">
                 <label>Parent Category</label>
                        <select class="form-control" name="category" id="category" data-url="{{ url('api/dropdown')}}" >

                            @foreach($categories as $category)
                                <option value="{{ $category->id }}" {{$category->category}}</option>
                            @endforeach
                        </select>


                    <br>
                </div>


                    <div class="form-group">
                        <label>Sub-Category Category</label>
                        <select class="form-control" name="cat_id" id="sub_category">
                            <option value=""></option>
                        </select>
                        @if($errors->has('cat_id'))
                            <span class="help-block">{{ $errors->first('cat_id') }}</span>
                        @endif
                    </div>
                    <br>

这是我的产品型号

<?php

namespace App;

use App\ProductPhoto;
use App\Brand;
use App\Category;
use Illuminate\Database\Eloquent\Model;

class Product extends Model {

protected $table = 'products';

protected $fillable = [
    'product_name',
    'product_qty',
    'product_sku',
    'price',
    'reduced_price',
    'cat_id',
    'featured',
    'brand_id',
    'description',
    'product_spec',
];

//protected $gaurded = ['id'];


/**
 * One Product can have one Category.
 *
 * @return \Illuminate\Database\Eloquent\Relations\HasOne
 */
public function category() {
    return $this->hasOne('App\Category', 'id');
}


// do same thing above for category() if you want to show what category a certain product is under in products page.

/**
 * A Product Belongs To a Brand
 *
 * @return \Illuminate\Database\Eloquent\Relations\HasOne
 */
public function brand() {
    return $this->belongsTo('App\Brand');
}


/**
 * Save a Product to the ProductPhoto instance.
 *
 * @param ProductPhoto $ProductPhoto
 * @return Model
 */
public function addPhoto(ProductPhoto $ProductPhoto) {
    return $this->photos()->save($ProductPhoto);
}


/**
 * One Product can have many photos.
 *
 * @return \Illuminate\Database\Eloquent\Relations\HasMany
 */
public function photos() {
    return $this->hasMany('App\ProductPhoto');
}


/**
 * Return a product can have one featured photo where "featured" column = true (or 1)
 *
 * @return mixed
 */
public function featuredPhoto() {
    return $this->hasOne('App\ProductPhoto')->whereFeatured(true);
}


/**
 * Show a product when clicked on (Admin side).
 *
 * @param $id
 * @return mixed
 */
public static function LocatedAt($id) {
    return static::where(compact('id'))->firstOrFail();
}


/**
 * Show a Product when clicked on.
 *
 * @param $product_name
 * @return mixed
 */
public static function ProductLocatedAt($product_name) {
    return static::where(compact('product_name'))->firstOrFail();
}


}

---

我成功了我只需要这样做

<div class="form-group">
             <label>Parent Category</label>
                    <select class="form-control" name="category" id="category" data-url="{{ url('api/dropdown')}}" >
                        <option value=""></option>
                        @foreach($categories as $category)
                            <option value="{{ $category->id }}" {{$product->Category->parent->id == $category->id ? "selected" : "" }}>{{ $category->category}}</option>
                        @endforeach
                    </select>


                <br>
            </div>


父类别
@foreach（$categories作为$category）
类别->父级->id=$Category->id？“选定”：“}}>{{$category->category}
@endforeach


我成功了我只需要这么做

<div class="form-group">
             <label>Parent Category</label>
                    <select class="form-control" name="category" id="category" data-url="{{ url('api/dropdown')}}" >
                        <option value=""></option>
                        @foreach($categories as $category)
                            <option value="{{ $category->id }}" {{$product->Category->parent->id == $category->id ? "selected" : "" }}>{{ $category->category}}</option>
                        @endforeach
                    </select>


                <br>
            </div>


父类别
@foreach（$categories作为$category）
类别->父级->id=$Category->id？“选定”：“}}>{{$category->category}
@endforeach


能否打印编辑刀片页的开头（$categories）及其显示数据？能否创建plnkr或完整代码？能否打印编辑刀片页的开头（$categories）及其显示数据？能否创建plnkr或完整代码？
<div class="form-group">
             <label>Parent Category</label>
                    <select class="form-control" name="category" id="category" data-url="{{ url('api/dropdown')}}" >
                        <option value=""></option>
                        @foreach($categories as $category)
                            <option value="{{ $category->id }}" {{$product->Category->parent->id == $category->id ? "selected" : "" }}>{{ $category->category}}</option>
                        @endforeach
                    </select>


                <br>
            </div>