How to create dateComponents from Date stored in CoreData

问题

I am trying to create dateComponents from Date stored in CoreData from UIDatePicker. However, I am not able to make it. I am first converting Date which is stored in editnotes?.sSelectedDate into dateComponents and then using the dateComponents for triggering my notifications.

Here is what I am doing:

 var date = Date()
        if let editnote = editnotes
        {
           date = editnote.sSelectedDate
        }
        else
        {
            print("nil")
        }
        let calendar = NSCalendar.current
        let unitFlags = Set<Calendar.Component>([.day, .month, .year, .hour, .minute])
        let anchorComponents = calendar.dateComponents(unitFlags, from: date)
        var dateInfo1 = DateComponents()
        dateInfo1.day = anchorComponents.day
        dateInfo1.month = anchorComponents.month
        dateInfo1.hour = anchorComponents.hour
        dateInfo1.minute = anchorComponents.minute
        dateInfo1.year = anchorComponents.year
        let trigger = UNCalendarNotificationTrigger(dateMatching:dateInfo1, repeats: false)

I am doing this:

if let editnote = editnotes
        {
           date = editnote.sSelectedDate
        }
        else
        {
            print("nil")
        }

to unwrap the optional but it's not working still. Continue reading!

I know I can use anchorComponents but that wasn't working so I copied those into a new DataComponents instance.

I am trying to print the what is stored indateInfo1.hour and I get

Optional(2)

I reckon this is the reason why dateComponents is not working for triggering notifications at scheduled time. Help will be appreciated?

回答1:

Explicit cast it like this

let anchorComponents = calendar.dateComponents(unitFlags, from: date) as! DateComponents

回答2:

You'r using anchorComponents.days / .hours / .days / .minutes it's all optional. Instead, I'd used initialiser for DateComponents where you explicitly set your properties you needed. But I think you'r just doing something wrong and that's why notification not working and the reason is not date. You can simply check it by setting from date to current date plus few seconds to see whether you'll get notification or not

来源：https://stackoverflow.com/questions/48244556/how-to-create-datecomponents-from-date-stored-in-coredata