绑定的领域数据库,但结果集为空

class StopRealm: Object {

    @objc dynamic var stop_id = 0
    @objc dynamic var stop_code = ""
    @objc dynamic var stop_name = ""
    @objc dynamic var stop_desc = ""
    @objc dynamic var stop_lat = 0.0
    @objc dynamic var stop_lon = 0.0
    @objc dynamic var location_type = 0.0
    @objc dynamic var parent_station = ""

}

我试着像这样加载数据库:

let config = Realm.Configuration( fileURL: Bundle.main.url(forResource: "StopsRealm", withExtension: "realm"), readOnly: true)
        let realm = try! Realm(configuration: config)
        let results = realm.objects(StopRealm.self)
        print(results)

然而,这留给我一个空的结果集。你知道怎么修吗?

更新:

let stop_id = RealmOptional<Int>()
    @objc dynamic var stop_code: String? = nil
    @objc dynamic var stop_name: String? = nil
    @objc dynamic var stop_desc: String? = nil
    let stop_lat = RealmOptional<Double>()
    let stop_lon = RealmOptional<Double>()
    let location_type = RealmOptional<Int>()
    @objc dynamic var parent_station: String? = nil