在同一模型上雄辩的亲子关系

Question

我有一个模型CourseModule，每个项目都与相同的模型相关。

Database Structure:

Relation in Model:

    public function parent()
    {
        return $this->belongsTo('App\CourseModule','parent_id')->where('parent_id',0);
    }

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

我尝试了以下内容，但它只返回一个级别的关系。

Tried:

CourseModule::with('children')->get();

我正在尝试创建一个类似于以下的json输出，

Expected Output:

[
  {
    "id": "1",
    "parent_id": "0",
    "course_id": "2",
    "name": "Parent",
    "description": "first parent",
    "order_id": "1",
    "created_at": "-0001-11-30 00:00:00",
    "updated_at": "-0001-11-30 00:00:00",
    "children": [
      {
        "id": "2",
        "parent_id": "1",
        "course_id": "2",
        "name": "Child 1",
        "description": "child of parent",
        "order_id": "2",
        "created_at": "-0001-11-30 00:00:00",
        "updated_at": "-0001-11-30 00:00:00",
        "children": [
          {
            "id": "3",
            "parent_id": "2",
            "course_id": "2",
            "name": "Child2",
            "description": "child of child1",
            "order_id": "2",
            "created_at": "-0001-11-30 00:00:00",
            "updated_at": "-0001-11-30 00:00:00",
            "children": [
              {
                "id": "4",
                "parent_id": "3",
                "course_id": "2",
                "name": "Child 3",
                "description": "child of child 2",
                "order_id": "2",
                "created_at": "-0001-11-30 00:00:00",
                "updated_at": "-0001-11-30 00:00:00",
                "children": []
              }
            ]
          }
        ]
      }
    ]
  }
]

我不明白如何获取内部子对象。

Answer 1

如果您有这样的未知深度，则必须以递归方式获取子项。

另一种选择是使用嵌套集模型而不是邻接列表模型。对于嵌套集，您可以使用类似baum/baum包的内容来使用Laravel。

“嵌套集是实现有序树的智能方法，允许快速，非递归查询。” - https://github.com/etrepat/baum

使用这个包你可以使用像getDescendants这样的方法来获取所有子项和嵌套子项，并使用toHierarchy来获得完整的树层次结构。

Wikipedia - Nested Set Model

Baum - Nested Set pattern for Laravel's Eloquent ORM

Managing Hierarchical Data in MySQL

Answer 2

您应该在子关系中使用with('children')，在父关系中使用with('parent')。

为了使您的代码递归：

public function parent()
{
    return $this->belongsTo('App\CourseModule','parent_id')->where('parent_id',0)->with('parent');
}

public function children()
{
    return $this->hasMany('App\CourseModule','parent_id')->with('children');
}

注意：确保您的代码具有某些或其他退出条件，否则它将以永无止境的循环结束。

Answer 3

here是可以帮助你的答案

我认为你必须以递归方式检索整棵树：

$data = CourseModule::with('child_rec');

Recursive function

这可以根据您的要求帮助您，

public function child()
{
   return $this->hasMany('App\CourseModule', 'parent');
}
public function children_rec()
{
   return $this->child()->with('children_rec');
   // which is equivalent to:
   // return $this->hasMany('App\CourseModule', 'parent')->with('children_rec);
}
// parent
public function parent()
{
   return $this->belongsTo('App\CourseModule','parent');
}

// all ascendants
public function parent_rec()
{
   return $this->parent()->with('parent_rec');
}

Answer 4

你可以随时创建自己的递归函数，在我的例子中，我做的代码如下。

<?php
declare(strict_types=1);

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Akmeh\Uuid;

/**
 * Class Location
 * @package Domain\Models
 */
class Location extends Model
{
    use Uuid;

    /**
     * Indicates if the IDs are auto-incrementing.
     *
     * @var bool
     */
    public $incrementing = false;
    public $timestamps = false;

    /**
     * @param string $id
     * @param array $tree
     * @return array
     */
    public static function getTree(string $id, array $tree = []): array
    {
        $lowestLevel = Location::where('id', $id)->first();

        if (!$lowestLevel) {
            return $tree;
        }

        $tree[] = $lowestLevel->toArray();

        if ($lowestLevel->parent_id !== 0) {
            $tree = Location::getTree($lowestLevel->parent_id, $tree);
        }

        return $tree;

    }

}

Answer 5

型号功能：

public function Children()
{ 
    return $this->hasMany(self::class, 'Parent', 'Id')->with('Children');
} 

控制器功能：

Menu::with("Children")->where(["Parent" => 0])->get(); 

Answer 6

你的模特关系应该是这样的

     // parent relation
     public function parent(){

        return $this->belongsTo(self::class , 'parent_id');
    }
    //child relation
     public function children()
    {
        return $this->hasMany(self::class ,'parent_id');
    }
    public function ascendings()
    {
        $ascendings = collect();

        $user = $this;

        while($user->parent) {
            $ascendings->push($user->parent);

            if ($user->parent) {
                $user = $user->parent;
            }
        }

        return $ascendings;
    }



    public function descendings()
    {
        $descendings = collect();
        $children = $this->children;

        while ($children->count()) {

            $child = $children->shift();

            $descendings->push($child);

            $children = $children->merge($child->children);

        }
        return $descendings;
    }