具有多个 sortDescriptors 和 Bool 过滤器的 Swift fetchRequest

Question

我正在从核心数据中获取。我有一个 bool 值属性，它与时间属性一起保存。我需要返回 bool 为真的日期数组。我无法让它工作，我要么得到一组空日期，要么崩溃。

func datesWithCompleteHBI() -> [Date] {

  let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
  fetchRequest.resultType = .dictionaryResultType
  fetchRequest.propertiesToFetch = ["savedTime", "harveyBradshawIndexComplete"]

  let timeSort = NSSortDescriptor(key: "savedTime", ascending: false)
  let hbiSort = NSSortDescriptor(key: "harveyBradshawIndexComplete", ascending: false)
  fetchRequest.sortDescriptors = [timeSort, hbiSort]

  let messageKey = true
  fetchRequest.predicate = NSPredicate(format: "harveyBradshawIndexSaveLevel = %@", messageKey as CVarArg)

  var dates = [Date]()
  do {

      let results = try managedObjectContext.fetch(fetchRequest) as! [[String:Date]]

      dates = results.flatMap { $0["savedTime"]}

     } catch let error as NSError {
       print("Could not fetch \(error), \(error.userInfo)")

    }

 print("hbi date array \(dates)")
 return dates
 }
}

Answer 1

如果您要返回一个 Date 和一个 Bool，则返回值不能是 [[String:Date]]

let results = try managedObjectContext.fetch(fetchRequest) as! [[String:Any]]

不是在代码中过滤项目，而是在谓词中添加过滤条件

fetchRequest.predicate = NSPredicate(format: "harveyBradshawIndexSaveLevel = %@ AND savedTime == TRUE", messageKey as CVarArg)

现在 results 包含过滤后的项目。