DateFormatter dateFromString Always Returns nil in swift 3

Question

Due to some reason fail to convert a string to a NSDate.

This is my date converting code:

 let kSQLiteDateFormat : String = "yyyy/MM/dd HH:mm:ss Z"
let dateFormat = [kSQLiteDateFormat,
"dd MM, yyyy",
"MMM-yyyy",
"yyyy-MM-dd",
"yyyy-12",
"yyyy/MM/dd",
"yyyy/mm/dd",
"yyyy-MM-dd HH:mm:ss",
"yyyy-MM-dd HH:mm:ss Z",
"yyyy-MM-dd HH:mm:ss K",
"yyyy-MM-dd HH:mm:ss ZZ",
"yyyy/MM/dd hh:mm a",
"MM/dd/yyyy",
"MM/dd/yyyy HH:mm:ss Z",
"h:mm a",
"hh:mm a",
"yyyy/MM/dd HH:mm:ss Z",
"yyyy/MM/dd h:mm a",
"MM/dd/yyyy h:mm a",
"yyyy-MM-dd h:mm a",
"yyyy-MM-dd'T'hh:mm:ss",
"yyyy/MM/dd h a",
"yyyy-MM-dd'T'HH:mm:ss","dd MMM, yyyy","dd-MM-yyyy HH:mm", "EEE, MMM dd","MM/dd/yyyy hh:mm:ss a"]


if let dateString : String = dateString as String? {
        let dateFormatter : DateFormatter = DateFormatter()
        for format in dateFormat {

            dateFormatter.dateFormat =  format
            if  let date : NSDate = (dateFormatter.date(from: dateString)! as NSDate) {
                return date
            }
        }
    }
    return nil

every time return nil

`dateFormat` needs to match the dateString. But there are plenty and plenty of possibilities. You can try the most common, but it doesn't mean it will works. What's `dateString`. — Larme, Jul 24 '17 at 13:55
`dateFormatter.date(from: dateString)` returns a `Date`, not an `NSDate` — Mike M, Jul 24 '17 at 14:02
The last one `"MM/dd/yyyy hh:mm:ss a"` should have done the trick, at least for this one (could be that month and day are inverted for another date). — Larme, Jul 24 '17 at 14:24

Martin R · Accepted Answer · 2017-07-24T14:47:44.767

The forced unwrapping in

if  let date : NSDate = (dateFormatter.date(from: dateString)! as NSDate) {
    return date
}

makes the program crash if dateString does not match the date format and dateFormatter.date(from: dateString) returns nil.

What you probably want is

if let date = dateFormatter.date(from: dateString) {
    return date
}

or, if you really need an NSDate and not a Date:

if let date = dateFormatter.date(from: dateString) {
    return date as NSDate
}

In addition, you might want to set the formatter's locate to "POSIX"

dateFormatter.locale = Locale(identifier: "en_US_POSIX")

in order to avoid a dependency on the user's regional preferences, compare DateFormatter doesn't return date for "HH:mm:ss".

setting locale fixed the crashes that happened randomly in my apps — titan, Feb 18 '20 at 09:11

score 4 · Answer 2 · answered Oct 01 '18 at 16:06

4

I found if you choose to use format like "MM/dd/yyyy hh:mm:ss" instead of "MM/dd/yyyy HH:mm:ss", you will get nil if your hour great than 12. please notice the difference of the hh and HH .

so this format "MM/dd/yyyy HH:mm:ss" should work.

answered Oct 01 '18 at 16:06

junliang lin

41
1

score 0 · Answer 3 · answered Jul 24 '17 at 14:11

0

From your code it can return nil only in this line

return nil

and the means that this this check returns false

if let dateString : String = dateString as String?

check your dateString variable maybe it is nil.

answered Jul 24 '17 at 14:11

Narek Simonyan

572
1
7
18

my detestring is "06/02/2017 03:05:12 PM" – Retoqa Retoqa Jul 24 '17 at 14:15
can you paste here the whole function, full code which you used to get the date? – Narek Simonyan Jul 24 '17 at 14:16
class func dateFromString(dateString : String) -> NSDate? { if let dateString : String = dateString as String? { let dateFormatter : DateFormatter = DateFormatter() for format in dateFormat { dateFormatter.dateFormat = format if let date : NSDate = (dateFormatter.date(from: dateString)! as NSDate) { return date } } } return nil } – Retoqa Retoqa Jul 24 '17 at 14:20
calling a function NSDate.dateFromString(dateString: dateAssigned) – Retoqa Retoqa Jul 24 '17 at 14:20
Why you are trying to check if dateString is not nil when you dateString parameter not a nullable String? remove this line if let dateString : String = dateString as String? { – Narek Simonyan Jul 24 '17 at 15:08

DateFormatter dateFromString Always Returns nil in swift 3

3 Answers3