使用Core Data设置日期选择器的初始值

Question

I have created two datepickers in which the user can enter their desired date and time.

When the user clicks the save button, the entered values are saved into Core Data using the following code:

    let dateFormatter = NSDateFormatter()
    dateFormatter.dateStyle = NSDateFormatterStyle.MediumStyle
    dateFormatter.timeStyle = NSDateFormatterStyle.NoStyle

    let timeFormatter = NSDateFormatter()

    timeFormatter.dateStyle = NSDateFormatterStyle.NoStyle
    timeFormatter.timeStyle = NSDateFormatterStyle.ShortStyle

    dateOfEntry = dateFormatter.stringFromDate(entryDate.date)  //entryDate is the name of the IBOutlet of the first date picker.

    timeStarted = timeFormatter.stringFromDate(startTime.date)  //startTime is the name of the IBOutlet of the second date picker.

This saves the date as : Nov 4, 2015 And the time as: 11:15 AM Which I then save into Core Data using

 entry.setValue(dateOfEntry, forKey: "date")

 entry.setValue(timeStarted, forKey: "startTime")

I was wondering if it is possible for me to use these stored values to later set the initial values of a separate set date pickers when the user opens a different view controller.

Answer 1

At the moment you're taking date and time selections that people have made with the picker and converting these to a string, and saving in your core data model as two strings.

A possible problem with this approach is that stringFromDate uses local settings on the device (country, language) to format that string, so for example people running the app in the US will have a different format than people in Germany.

Probably what you want to do is combine the selections from your date picker and your time picker into a single NSDate , and then save that combined date directly in core data.

It's a little bit more work upfront when you're creating the entity, but you get some benefits:

• don't have to worry about locales from different regions
• if you ever wanted you can now apply sorting of values based on your date attribute
• makes it a lot easier to populate your pickers based off a date returned from a query.