php - Eloquent Parent-Child relationship on same model

Question

I have a model CourseModule, and each of the items are related to the same model.

Database Structure:

Relation in Model:

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

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

I tried the following, but it returns only a single level of relation.

Tried:

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

I'm trying to create a json output like the following,

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": []
              }
            ]
          }
        ]
      }
    ]
  }
]

I don't understand how to get the inner child objects.

Answer 1

You should use with('children') in the children relation and with('parent') in the parent relations.

For your code to be recursive:

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

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

Note: Make sure your code has some or the other exit conditions otherwise it will end up in a never ending loop.