保存后无法从CoreData获取更新数据

Question

我引用programming guide将数据保存到CoreData，而我的实体代码是类别/扩展名（pic）

我使用performBackgroundTask来保存数据。 虽然，我保存后无法获取数据。 我必须强制关闭一个应用程序，然后再次重新打开它，我可以获取保存数据。

以下是我的代码。

将数据保存到CoreData的方法：

var container: NSPersistentContainer? =
    (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer

private func updateDatabase() {

    container?.performBackgroundTask { [weak self] context in

        if let name = self?.employeeName.text {
            _ = try? Employee.findOrCreateEmployee(matching: name, in: context)
        }

        var date = (self?.startDate)!
        let end = (self?.endDate)!

        let fmt = DateFormatter()
        fmt.dateFormat = "MM/dd"

        while date <= end {
            //print(fmt.string(from: date))

            _ = try? Shift.findOrCreateShift(byEmployee: (self?.employeeName1.text)!, date: fmt.string(from: date), assignment: nil, in: context)
            date = Calendar.current.date(byAdding: .day, value: 1, to: date)!
        }

        try? context.save()
    }
}

从CoreData获取数据的方法：

var container: NSPersistentContainer? =
    (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer {
    didSet { updateUI() }
}

private func updateUI() {
    if let context = container?.viewContext {
        let employeeRequest: NSFetchRequest<Employee> = Employee.fetchRequest()
        employeeRequest.sortDescriptors = [NSSortDescriptor(
            key: "created",
            ascending: true,
            )]
        employees = try? context.fetch(employeeRequest)

        let shiftsRequest: NSFetchRequest<Shift> = Shift.fetchRequest()
        shiftsRequest.sortDescriptors = [ NSSortDescriptor(
            key: "date",
            ascending:true
            )]
        shifts = try? context.fetch(shiftsRequest)

    }
}

有没有人有任何建议？

感谢。