使用NSPredicate過濾fetchRequest年/月

Question

我有一個應用程序，其中包含多個時間條目，並將日期另存爲NSDate。

我想使用一個獲取請求來篩選我從別的地方獲得的某個年份和月份。我如何使用NSPredicate過濾一年和一個月？

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

更新

使用幫助Raki酒指出，我想出了下面的代碼：

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!) 

和謂詞：

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

我得到一個SIGABRT與以下消息：

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

Xcode建議我加「as！ CVarArg」

更新2

下斷言現在的工作：

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

Answer 1

你不能斷言這個樣子，但你可以創建你的月和一年兩Dates其開始月份的一天，

現在你需要簡單地這樣預測：

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

編輯：如果你不知道如何爲startDateOfMonth和endDateOfMonth創建日期，那麼你可以使用DateComponents創建它。

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!)