php - Laravel 5.3 中为 foreach() 提供的参数无效

Question

我不知道它到底是如何工作的，所以这就是我问的原因。我仍在开发公告板系统，现在我希望在每个类别下都有一个子类别。

例如:

我在 LaraCasts 上使用以下线程完成了此操作: https://laracasts.com/discuss/channels/eloquent/eloquent-getting-subcategories-from-the-categories

现在我的 IndexController 看起来像这样:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Thread;
use App\Chat;
use App\Category;


class IndexController extends Controller
{
    /**
     * Show the application dashboard.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        $threads = Thread::all()->toArray();
        $chats = Chat::orderBy('id', 'DESC')->take(50)->with('author')->get();
        $categories = Category::with('sub_category')->get();

        return view('index', compact('threads','chats','categories'));
    }

 }

这是我的类别模型:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Category extends Model
{


    public function sub_category()
    {
        return $this->belongsTo(self::class, 'parent_id', 'id');
    }

    public function parent_category()
    {
        return $this->hasMany(self::class, 'id', 'parent_id');
    }


}

我的观点(index.blade.php):

  @foreach($categories as $category)
      <div class="col-md-8">
         <div class="panel panel-primary">
            <div class="panel-heading"><i class="fa fa-angle-right" aria-hidden="true"></i>  {{ $category->caption }}</div>
            <div class="panel-body">



        @foreach($category->sub_category as $sub_category)

               <div class="row forum-row">

                  <div class="col-xs-12 col-md-8 col-sm-8">

                     <div class="hidden-xs visible-sm visible-lg visible-md pull-left forum-icon-read">
                     <i class="fa fa-comment"></i>
                     </div>
                     <a href="#">{{ $sub_category->caption }}</a><br>
                     <small>{{ $sub_category->desc }}</small>

                  </div>

                  <div class="col-xs-12 col-md-4 col-sm-4 forum-latest-container">
                     <p class="forum-data cutoff"><a href="#">Test</a></p>
                     <small>
                     door <a class="Donateur" href="/user-Sygun">Sygun</a>
                     <p class="forum-data">
                     2 minuten geleden </p>
                     </small>
                  </div>

               </div>
                @endforeach


            </div>
         </div>
      </div>
       @endforeach

我还有两个数据库表:

• 子类别(id、标题、parent_id、min_rank、desc)

• 类别(id、标题、min_rank、desc)

我收到的错误消息:

Invalid argument supplied for foreach()

你能告诉我实现这一目标的正确方法是什么吗？

Answer 1

创建两个名为Category和SubCategory的模型。

在类别模型中

public function subcategories()
{
    return $this->hasMany('App\SubCategory', 'parent_id');
}

在子类别模型中

public function parent_category()
{
    return $this->belongsTo('App\Category', 'parent_id');
}

然后在你的 Controller 中查询它，如下所示:

$categories = Category::with('subcategories')->get();

希望您的 foreach 能够正常工作。