ios - 使用NSPredicate过滤年/月的fetchRequest

Question

我有一个应用程序，其中包含多个时间条目，并且日期保存为NSDate。

我想使用获取请求来过滤从其他地方获取的特定年份和月份。如何使用NSPredicate过滤一年和一个月？

let predicate = NSPredicate(format: "%K == %D && %K == %D", ???, selectedMonth, ???, selectedYear)

更新

使用帮助，Raki指出了以下代码:

var dateComp = DateComponents()
dateComp.year = Int(selectedYear)
dateComp.month = Int(selectedMonth)
dateComp.day = 1

let calendar = Calendar.current
let firstDayOfTheMonth = calendar.date(from: dateComp)

var oneMonth = DateComponents()
oneMonth.month = 1
let beginningOfNextMonth = calendar.date(byAdding: oneMonth, to: firstDayOfTheMonth!)

和谓词:

let predicate = NSPredicate(format: "date >= %@ AND date < %@", firstDayOfTheMonth as! CVarArg, beginningOfNextMonth as! CVarArg)

我收到带有以下消息的SIGABRT:

Could not cast value of type 'Foundation.Date' (0x1073a0ae0) to 'Swift.CVarArg' (0x1196851c8).

Xcode建议我添加“as!CVarArg”

更新2

以下谓词现在起作用:

let predicate = NSPredicate(format: "%K >= %@ && %K < %@", "date", firstDayOfTheMonth! as NSDate, "date", beginningOfNextMonth! as NSDate)

Answer 1

您无法像这样进行谓词，但是您可以从月份和年份中创建两个Dates，分别从月份的月日和月份的结束日开始。

现在，您需要像这样简单地进行谓词。

let predicate = NSPredicate(format: "%K >= %@ && %K <= %@", "DateAttribute", startDateOfMonth as NSDate, "DateAttribute", endDateOfMonth as NSDate)

编辑:如果您不知道如何为 startDateOfMonth和 endDateOfMonth创建日期，则可以使用 DateComponents创建日期。

let selectedMonth = 11
let selectedYear = 2015
var components = DateComponents()
components.month = selectedMonth
components.year = selectedYear
let startDateOfMonth = Calendar.current.date(from: components)

//Now create endDateOfMonth using startDateOfMonth
components.year = 0
components.month = 1
components.day = -1
let endDateOfMonth = Calendar.current.date(byAdding: components, to: startDate!)