Question

我对Swift还是相当陌生，希望有人知道答案-我尝试的任何方法似乎都无效！

我有一个Swift应用程序，该应用程序具有一个名为“ Drink”的Core Data实体，该实体具有2个键：一个日期和一个名为“ drinkWater”的实体，当按下按钮时，该实体存储值“ 1”。

我正在尝试编写一个单独的函数，在该函数中，我可以检查是否存在今天的日期条目，如果存在，请执行一个操作（在这种情况下，请更改imageview）。

我意识到以下并不是答案，但就我所知！基本上，我可以根据DrinkWater的值来获取所有条目（这需要在我猜的日期之前？），并且可以将今天的所有日期打印到控制台上。现在我被卡住了...

private func updateMyImageView() {

    let appDelegate = UIApplication.shared.delegate as! AppDelegate

    let context = appDelegate.persistentContainer.viewContext

    let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Drink")
    request.predicate = NSPredicate(format: "drinkWater = %@", "1")
    request.returnsObjectsAsFaults = false

    do {
        let result = try context.fetch(request)
        for data in result as! [NSManagedObject] {
            print(data.value(forKey: "timestamp") as! Date)

        }

    } catch {

        print("Failed")
    }

    let dateNow = Date()

    print("Date is \(dateNow)")

}

这将返回：

2018-12-29 01:27:27 +0000

日期是2018-12-29 12:21:21 +0000

任何将其全部转换为正确功能的想法将不胜感激！！

Answer 1

您需要在复合谓词中使用从开始日期到结束日期（午夜至午夜）的日期范围。这是基于类似的question

的解决方案

var calendar = Calendar.current
calendar.timeZone = NSTimeZone.local

let dateFrom = calendar.startOfDay(for: Date())
let dateTo = calendar.date(byAdding: .day, value: 1, to: dateFrom)

let fromPredicate = NSPredicate(format: "timestamp >= %@", dateFrom as NSDate)
let toPredicate = NSPredicate(format: "timestamp < %@", dateTo! as NSDate)
let waterPredicate = NSPredicate(format: "drinkWater = %@", "1")

let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Drink")
request.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [waterPredicate, fromPredicate, toPredicate])

Answer 2

感谢您的所有帮助。我已经全部工作了。我的最终代码是：

let appDelegate = UIApplication.shared.delegate as! AppDelegate

        let context = appDelegate.persistentContainer.viewContext

        var calendar = Calendar.current
        calendar.timeZone = NSTimeZone.local

        let dateFrom = calendar.startOfDay(for: Date())
        let dateTo = calendar.date(byAdding: .day, value: 1, to: dateFrom)

        let fromPredicate = NSPredicate(format: "timestamp >= %@", dateFrom as NSDate)
        let toPredicate = NSPredicate(format: "timestamp < %@", dateTo! as NSDate)
        let waterPredicate = NSPredicate(format: "drinkWater = %@", "1")

        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Drink")
        request.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [waterPredicate, fromPredicate, toPredicate])

        do {
            let result = try context.fetch(request)
            for data in result as! [NSManagedObject] {
                print(data.value(forKey: "timestamp") as! Date)

              drinkMoreButton.setBackgroundImage(UIImage(named: "watericonselected.png"), for: UIControlState.normal)
            }

        } catch {

            print("Failed")
        }

使用今天的日期和执行功能检查核心数据以获取条目

2 个答案: