swift – 使用Alamofire和Objectmapper,整数值始终为零

class Category: Object,Mappable {

dynamic var id: Int = 0
dynamic var name = ""
dynamic var thumbnail = ""
var children = List<Category>()


override static func primaryKey() -> String? {
    return "id"
}


required convenience init?(_ map: Map) {
    self.init()
}

func mapping(map: Map) {
    id <- map["id"]
    name <- map["name"]
    thumbnail <- map["thumbnail"]
    children <- map["children"]
}

}

而我正在使用这样的Alamofire

Alamofire.request(.GET,url).responseArray { (response: Response<[Category],NSError>) in

        let categories = response.result.value

        if let categories = categories {
            for category in categories {
                print(category.id)
                print(category.name)
            }
        }
    }

id永远为零,我不知道为什么？