Formatting a date from a string in swift [duplicate] - ios

Question

This question already has answers here:
How can I parse / create a date time stamp formatted with fractional seconds UTC timezone (ISO 8601, RFC 3339) in Swift?
(13 answers)
Closed 3 years ago.
i have the following date coming from a server 2019-09-05T10:37:49.494Z as a string and i need to parse this and convert it to a format like this Fri September 13,2019 12:36 AM and back to a string again:
i found multiple question links but none of them are working for me Question One
Question Two
it tried doing this:
let dateFormatterGet = DateFormatter()
let dateFormatterPrint = DateFormatter()
var rawDate = "2019-09-05T10:37:49.494Z"
dateFormatterGet.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
dateFormatterPrint.dateFormat = "E, d MMM yyyy HH:mm"
var formattedDate = "Error Formatting date"
if let date = dateFormatterGet.date(from: rawDate) {
formattedDate = dateFormatterPrint.string(from: date)
print("Formatted Date : \(formattedDate)")
}else {
print("There was an error decoding the string")
}
this fails printing the error message, what am i doing wrong and how can i fix it?

Answer 1

You are almost there.
A small tip playing with (NS)DateFormatter put the dateFormat above/under the date string.
yyyy-MM-dd'T'HH:mm:ssZ
2019-09-05T10:37:49.494Z
Then, add "spaces" to align and separate them.
yyyy - MM - dd 'T' HH : mm : ss Z
2019 - 09 - 05 T 10 : 37 : 49 . 494Z
^ ^^^
I highlighted the missing ones. You need to tell the (NS)DateFormatter through the dateFormat how to interpret theses additional characters.
Let's check the documentation.
It's
Fractional Second - truncates (like other time fields) to the count of letters. (example shows display using pattern SSSS for seconds value 12.34567)
So using yyyy-MM-dd'T'HH:mm:ss.SSSZ should interpret them and fix your issue.
That's how you fix your issue. And it explained your error.
But since as pointed by #Zombie it's using a ISO format, use if available the ISO8601DateFormatter if possible (iOS10+)
If in future cases you don't have an ISO something format, you can use theses tips ;)

Answer 2

The format you provided seems like an iso 8601 date for this reason I would suggest using the ISO8601DateFormatter
You can specify the options to match your string
here is an example
let dateString = "2019-09-05T10:37:49.494Z"
let formatter = ISO8601DateFormatter()
formatter.formatOptions = [
.withDashSeparatorInDate,
.withFullDate,
.withFullTime,
.withFractionalSeconds,
.withColonSeparatorInTime
]
// "Sep 5, 2019 at 12:37 PM"
let date = formatter.date(from: dateString) ?? Date()
//"Thursday, September 5, 2019 at 12:37:49 PM"
let formattedDate = DateFormatter.localizedString(
from: date,
dateStyle: .full,
timeStyle: .medium
)

Answer 3

The problem is you don't tell dateFormatterGet how to parse milliseconds. Modify the dateFormat to:
dateFormatterGet.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"