在laravel中获取BadMethodCallException

Question

class Degree extends Eloquent{
    protected $table = 'degrees';
    public $timestamps = false;
    
    public function user()
    {
        return $this->belongsToMany('User', 'user_degree');
    }
    
    public function university()
    {
        return $this->belongsTo('University');
    }
    
    public function type()
    {
        return $this->belongsTo('DegreeType', 'degree_type_id');
    }
   


///////another model is//////

class DegreeType extends Eloquent{
    protected $table = 'degree_types';
    protected $fillable = ['name', 'approved'];
    public $timestamps = false;
    
    public function user()
    {
        return $this->belongsToMany('User', 'user_degree');
    }
}


//////and finally controller is ///////

foreach ($degreeTypeC as $param)
        {
            $u = $u->whereHas('degree', function($q) use($param){
                $q->whereHas('type', function($q) use($param){
                    $q->where('id', '=', $param);
                });
            });
        }

给出错误：

  

{“error”：{“type”：“BadMethodCallException”，“message”：“调用未定义的方法Illuminate \ Database \ Query \ Builder :: degree（）”，“file”：“/ var / www /供应商/ laravel /框架/ SRC /照亮/数据库/查询/ Builder.php”， “行”：2113}}

问题出在哪里？