Swift coreData - 格式化日期并在谓词中使用它 [英] Swift coreData - format date and use it in predicate

问题描述

小时。
我有一个名为Agendadate的实体和一个名为AgendaEvent的实体。
AgendaEvent与AgendaDate（agendaDates）有很多关系。

H. I have an entity called Agendadate and one called AgendaEvent. AgendaEvent has a many to many relation with AgendaDate (agendaDates).

在我的AgendaDate中我有一个对象日期（类型为Date）。

in my AgendaDate i have an object dates (of type Date).

我正在使用这样的谓词：

I'm using a predicate like so:

fetchRequest.predicate = NSPredicate(format: "ANY agendaDates.dates == %@", date as CVarArg)

我正在尝试设置日期格式：

I'm trying to format dates to have this:

dd MM yyyy而不是yyyy MM dd hh：mm：ss

"dd MM yyyy" instead of "yyyy MM dd hh:mm:ss"

我需要在谓词中比较两个日期但没有时间吗？
有可能吗？

I need to compare in the predicate two dates but without the time? is it possible?

UPDATE -----
这是我的功能更新，如你所知：

UPDATE----- Here's my function updated as you have suggested:

func agendaEventsWithDate(date: Date) -> NSFetchRequest<AgendaEvent>
{
    // create a fetch request that will retrieve all the AgendaEvents.
    let fetchRequest = NSFetchRequest<AgendaEvent>(entityName: "AgendaEvent")

    // set the predicate to only keep AgendaEvents where the related AgendaDate's date matches the passed in date.
    let cal = Calendar.current
    let startOfDay = cal.startOfDay(for: eventDate)
    let endOfDay = cal.date(byAdding: .day, value: 1, to: startOfDay)!
    print(startOfDay)
    print(endOfDay)
    // fetchRequest.predicate = NSPredicate(format: "ANY agendaDates.agendaDates == %@", date as CVarArg)
     fetchRequest.predicate = NSPredicate(format: "SUBQUERY(agendaDates, $a, $a.dates >= %@ AND $a.dates < %@).@count > 0",
                                startOfDay as NSDate, endOfDay as NSDate)

    return fetchRequest
}

这里是应该配置单元格的函数，只接受具有相同日期的事件：

and here's the function that should configure the cell and take just the events which have the same date of the selected date:

func configuringCell(cell: CalendarAgendaCell, indexPath: IndexPath) {
    for dates in calendar.selectedDates {
        for dateOfEvent in myEventDate {
            formatter.dateFormat = "dd MM yyyy"
            let dateToCompare = formatter.string(from: dates)
            formatter.dateFormat = "dd-MM-yyyy"
            let comparingDate = formatter.date(from: dateToCompare)!
            if dateOfEvent == dateToCompare {
                myTempEvents = try! context.fetch(agendaEventsWithDate(date: comparingDate))
                let myEvent = myTempEvents[indexPath.row]
                cell.configureCell(agendaEvent: myEvent)

            } else {
               // the array is empty

            }
        }
    }
}

推荐答案

不要为此目的使用自定义字符串格式。您想要获取
与Agendadate对象相关的所有条目，并在给定日期的同一天使用日期
。

Don't use a custom string format for that purpose. You want to fetch all entries which are related to an Agendadate object with a date on the same day as the given day.

所以你首先计算当天的开始和结束：

So you compute the start and end of that day first:

let date = Date()

let cal = Calendar.current
let startOfDay = cal.startOfDay(for: date)
let endOfDay = cal.date(byAdding: .day, value: 1, to: startOfDay)!

然后使用此SUBQUERY：

Then use this SUBQUERY:

let predicate = NSPredicate(format: "SUBQUERY(agendaDates, $a, $a.dates >= %@ AND $a.dates < %@).@count > 0",
                            startOfDay as NSDate, endOfDay as NSDate)

它测试 $ a.dates> = startDate AND $ a.dates<所有
相关对象的endDate ，如果条件中至少有一个匹配的
，则产生true。

It tests $a.dates >= startDate AND $a.dates < endDate for all related objects, and yields true if there is at least one matching the condition.

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