我创建了一个模型，并希望使用模型内部定义的函数获取与模型表相关的详细信息。

<?php namespace App\Models;
use CodeIgniter\Database\ConnectionInterface;
use CodeIgniter\Model;

class DepartmentModel extends Model
{
    protected $table = 'tbl_department';
    
    protected $primaryKey = 'id';

    protected $useAutoIncrement = true;

    protected $returnType     = 'array';

    protected $allowedFields = ['vchr_departmentName','int_divisionID', 'vchr_address'];
 

    protected $validationRules    = [];
    protected $validationMessages = [];
    protected $skipValidation     = false;
    
    public function getDeptID($userid)
    {
     
      $db = \Config\Database::connect();
      $builder=$db->table('tbl_department')
      $builder->select('tbl_department.id');
      $builder->join('tbl_employee','tbl_department.id=tbl_employee.int_departmentID');
      $builder->where('tbl_employee.int_userID',$userid);
      $res=$builder->get()->getRowArray();

      return $res['id'];

    }
    
    public function getDeptName($int_departmentID)
    {
    
     $result = $this->where('id',$int_departmentID)->find();
     return $result['vchr_departmentName'];
    
    }
    
}

可以在模型的类中编写函数吗？我可以使用$this来获取模型类的示例吗