iao_team/app/Http/Livewire/Courses.php

<?php
namespace App\Http\Livewire;
use Livewire\Component;
class Courses extends Component
{
    public $level_1 = [];
    public $level_2 = [];
    public $level_3 = [];

    public $level_1_id = 0;
    public $level_2_id = 0;
    public $level_3_id = 0;

    public $course_id = null;

    public function mount($course_id)
    {
        $this->course_id = $course_id;
        if ($this->course_id != null)
        {
            $c = \App\Models\Course::findOrFail($this->course_id);
            $ids = array_reverse($c->recursiveParent($c->parent_id, [$c->id]));
            foreach($ids as $ii => $i)
            {
                if ($ii == 0)
                {
                    $this->level_1_id = $i;
                }
                if ($ii == 1)
                {
                    $this->level_2_id = $i;
                }
                if ($ii == 2)
                {
                    $this->level_3_id = $i;
                }
            }

        }
    }

    public function updatedLevel1Id() {
        $this->emit('setCourse', null);
        $this->level_2_id = 0;
        $this->level_2 = [];
        $this->level_3_id = 0;
        $this->level_3 = [];
    }
    public function updatedLevel2Id() {
        $this->emit('setCourse', null);
        $this->level_3_id = 0;
        $this->level_3 = [];
    }
    public function updatedLevel3Id() {
        $this->emit('setCourse', null);
    }

    public function render()
    {
        $reset = false;
        if ($this->level_1_id > 0)
        {
            $this->level_2 = \App\Models\Course::where('parent_id', $this->level_1_id)->orderBy('name')->get();
            if (sizeof($this->level_2) == 0)
            {
                $this->emit('setCourse', $this->level_1_id);
                $reset = true;
            }
        }
        if ($this->level_2_id > 0)
        {
            $this->level_3 = \App\Models\Course::where('parent_id', $this->level_2_id)->orderBy('name')->get();
            if (sizeof($this->level_3) == 0)
            {
                $this->emit('setCourse', $this->level_2_id);
                $reset = true;
            }
        }
        if ($this->level_3_id > 0)
        {
            $this->emit('setCourse', $this->level_3_id);
            $reset = true;
        }
        $this->level_1 = \App\Models\Course::where('parent_id', null)->orderBy('name')->get();

        return view('livewire.courses');
    }
}