在带有 iCloud 的 CoreData 驱动应用程序中使用 NSSortDescriptor 和 NSFetchedResultsController 的自定义部分

Question

我在使用带有 iCloud 同步的 Core Data 在应用程序中实现自定义部分时遇到问题。

我制作了一个示例应用程序来说明我的问题：它在 CoreData 中有一个事件列表（使用 FRC 获取）

事件实体：

@objc(Event)
class Event: NSManagedObject {

@NSManaged var timeStamp: NSDate?
@NSManaged var name: String?
@NSManaged var sectionIdentifier :Int32

}

我已经根据项目的时间戳实现了自定义部分：

• 过去
• 今天
• 明天
• 接下来的 7 天
• 未来

• 没有日期

  enum SectionType:Int32{
  case inPast = 9
  case Today = 10
  case Tomorrow
  case Next7Days
  case InFuture
  case NotSet = 14
  
  func title()->String{
      switch self {
      case .inPast:
          return "In Past"
      case .Today:
          return "Today"
      case .Tomorrow:
          return "Tomorrow"
      case .Next7Days:
          return "Next 7 Days"
      case .InFuture:
          return "In Future"
      default:
          return "No due date"
      }
  }
  

  }

FRC 代码

   private var _fetchedResultsController: NSFetchedResultsController? = nil
var fetchedResultsController: NSFetchedResultsController {
    if _fetchedResultsController != nil {
        return _fetchedResultsController!
    }

    let fetchRequest = NSFetchRequest()
    let entity = NSEntityDescription.entityForName("Event", inManagedObjectContext: self.managedObjectContext!)
    fetchRequest.entity = entity
    fetchRequest.fetchBatchSize = 20

    let sortDescriptors = [
        NSSortDescriptor(key: "sectionIdentifier", ascending: true),
        NSSortDescriptor(key: "timeStamp", ascending: true)
    ]

    fetchRequest.sortDescriptors = sortDescriptors

    let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,
        managedObjectContext: self.managedObjectContext!,
        sectionNameKeyPath: "sectionIdentifier",
        cacheName:nil)

    aFetchedResultsController.delegate = self

    _fetchedResultsController = aFetchedResultsController

    var error: NSError? = nil
    if !_fetchedResultsController!.performFetch(&error) {
         abort()
    }

    return _fetchedResultsController!
}    

似乎一切正常，事件按 sectionIdentifier 分组。 但是，如果它现在与其他时区的设备同步，则由于时间差异，事件将被错误地分组。

使用瞬态属性会有所帮助，但是我不能使用 NSSortDescriptor 对部分进行排序。

有什么解决办法吗？我真的不想为每个部分填充数组等等。

亲切的问候

Answer 1

所以我通过实现一个瞬态属性解决了我的问题。

剩下的唯一问题是没有日期的事件被放在列表的顶部。 但我已经通过添加另一个属性 hasDate (Bool) 并添加第二个 NSSortDescriptor 来解决它

托管对象：

import Foundation
import CoreData

enum SectionType:String{
    case inPast = "10"
    case Today = "11"
    case Tomorrow = "12"
    case Next7Days = "13"
    case InFuture = "14"
    case NotSet = "15"

func title()->String{
    switch self {
    case .inPast:
        return "In Past"
    case .Today:
        return "Today"
    case .Tomorrow:
        return "Tomorrow"
    case .Next7Days:
        return "Next 7 Days"
    case .InFuture:
        return "In Future"
    default:
        return "No due date"
    }
}
}



@objc(Event)

class Event: NSManagedObject {

@NSManaged var timeStamp: NSDate?
@NSManaged var noDate: Bool
@NSManaged var name: String?

var sectionIdentifier :String? {
    get {
        var str : String

            if let aDate = self.timeStamp {
                if aDate.isToday() || aDate.isYesterday() {
                   str = SectionType.Today.rawValue
                } else if aDate.isTommorow() {
                     str = SectionType.Tomorrow.rawValue
                } else if aDate.isNext7Days() {
                     str = SectionType.Next7Days.rawValue
                } else if aDate.inPast(){
                     str = SectionType.inPast.rawValue
                } else {
                     str = SectionType.InFuture.rawValue
                }

            }else {
                 str = SectionType.NotSet.rawValue
            }

        return str
    }
    set {
        self.sectionIdentifier = newValue
    }
}



func setTime(date : NSDate?){
    self.willChangeValueForKey("timeStamp")
    self.setValue(date, forKey: "timeStamp")
    self.didChangeValueForKey("timeStamp")

    if let date = date {
        self.noDate = false
    }
}

class func keyPathsForValuesAffectingSectionIdentifier() -> NSSet {
    return  NSSet(object: "timeStamp")
}

}

FRC：

       private var _fetchedResultsController: NSFetchedResultsController? = nil
    var fetchedResultsController: NSFetchedResultsController {
        if _fetchedResultsController != nil {
            return _fetchedResultsController!
        }

        let fetchRequest = NSFetchRequest()
        let entity = NSEntityDescription.entityForName("Event", inManagedObjectContext: self.managedObjectContext!)
        fetchRequest.entity = entity
        fetchRequest.fetchBatchSize = 20

        let sortDescriptors = [
//            NSSortDescriptor(key: "sectionIdentifier", ascending: true),
            NSSortDescriptor(key: "noDate", ascending: true),
            NSSortDescriptor(key: "timeStamp", ascending: true)
        ]

        fetchRequest.sortDescriptors = sortDescriptors

        let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,
            managedObjectContext: self.managedObjectContext!,
            sectionNameKeyPath: "sectionIdentifier",
            cacheName:nil)

        aFetchedResultsController.delegate = self

        _fetchedResultsController = aFetchedResultsController

        var error: NSError? = nil
        if !_fetchedResultsController!.performFetch(&error) {
             abort()
        }

        return _fetchedResultsController!
    }