我正在将数据插入表中，其插入成功，
但是当我获取所有数据然后获取成功的实体数组时，
但是当我使用实体时，我检查实体的nil . 该属性是String类型，当我执行“Entity.attributeName”应用程序崩溃时，我使用选项var来存储属性值 .
错误是“libc abi.dylib：以NSException类型的未捕获异常终止”
当我检查已经检查实体对象时，我不明白为什么它崩溃了
请建议我如何在swift3中调试和处理这种类型的异常 .
/// fetch method to Fetch data
func fetchRecordsForEntity(_ entity: String, inManagedObjectContext managedObjectContext: NSManagedObjectContext) -> [NSManagedObject] {
// Create Fetch Request
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
fetchRequest.returnsObjectsAsFaults = false
// Helpers
var result = [NSManagedObject]()
do {
// Execute Fetch Request
let records = try managedObjectContext.fetch(fetchRequest)
if let records = records as? [CityEntity] {
result = records
}
} catch {
print("Unable to fetch managed objects for entity \(entity).")
}
return result
}
/// where app crash
let cityEntity:CityEntity? = self.allCity![indexPath.row]
let cityName:String? = cityEntity?.cn_city_name