ios - 使用 Core Data 获取存储的数据

Question

在我下面的代码中，我可以使用 Core Data 存储数据。我存储的数据是奖励。我如何从核心数据中获取奖励数据？每当有奖励已添加到该特定用户时，我如何在我的核心数据中获得总奖励？我为每个用户使用 loggedInUserHouseNumber。如何获取与 loggedInUserHouseNumber 相等的奖励数据和奖励总额？ .我想获得所有数据和总奖励等于登录用户门牌号任何人都可以提供答案吗？

 loggedInUserHouseNumber =  (UserDefaults.standard.value(forKey: "loggedInUserHouseNumber")  as! String)

获取请求代码

let appDelegate = UIApplication.shared.delegate as! AppDelegate
        let context = appDelegate.persistentContainer.viewContext
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "GroceryItem")
        request.returnsObjectsAsFaults = false


self.saveReward(reward: rewardInt)

保存数据代码:

func saveReward(reward: Int64){
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let groceryData = GroceryItem(context: context) // Link GroceryItem & Context
    groceryData.reward = reward
    groceryData.isSelected = false
    groceryData.houseNo = loggedInUserHouseNumber
    //        print("data:", groceryItem.name)
    print("ang reward nga na save: ", groceryData.reward)
    print("jelordrey")
    (UIApplication.shared.delegate as! AppDelegate).saveContext()
}

Answer 1

您需要使用NSPredicate 来查询特定的房子不，您可以尝试使用下面的示例代码。

let loggedInUserHouseNumber =  (UserDefaults.standard.value(forKey: "loggedInUserHouseNumber")  as! String)
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "GroceryItem")
//Create query 
request.predicate = NSPredicate(format: "houseNo = %@", loggedInUserHouseNumber ?? "")
 do {

       if let models = try context.fetch(request) as? [GroceryItem] {
        // You will get count 
        let count = models.count
        var total = 0
         for model in models {
            total = total + model. reward
       }

    }
   } catch let error {
        // Handle error
    }