How to convert a sting to a date, and back again, in swift?

Question

I receive a timestamp from a JSON request, and I want to format it to a user-friendly format. Both the input, as the desired output are of type 'String'.

The format of the input timestamp is: 2020-03-07T12:18:26.347Z

Using the following code, I try to convert it to the desired format. But it will just output the value of Date(), indicating that the output of formatter.date(from: date) is nil.

What am I missing?

func convertDate(date: String) -> String {

    let formatter = DateFormatter()
    formatter.dateFormat = "d-M-y, HH:mm"

    let convertedDate = formatter.date(from: date) ?? Date()

    return formatter.string(from: convertedDate)

}

https://www.hackingwithswift.com/example-code/system/how-to-convert-dates-and-times-to-a-string-using-dateformatter — Roland Lariotte, Apr 19 '20 at 08:41

score 1 · Answer 1 · answered Apr 19 '20 at 08:48

1

Your dateFormat doesn't match the format of your input string. You want something like:

formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"

answered Apr 19 '20 at 08:48

zpasternack

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score 0 · Accepted Answer · answered Apr 19 '20 at 08:57

After struggling with it for hours, this answer, together with the date format information found here, I figured it out. I did previously not describe to the dateformatter how the input string would look.

func convertDate(date: String) -> String {

    let dateFormatter = DateFormatter()

    // This is important - we set our input date format to match our input string
    // if the format doesn't match you'll get nil from your string, so be careful
    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"

    //`date(from:)` returns an optional so make sure you unwrap when using.
    let dateFromString: Date? = dateFormatter.date(from: date)

    let formatter = DateFormatter()
    formatter.dateFormat = "dd-MM-yyyy, HH:mm"

    //Using the dateFromString variable from before.
    let stringDate: String = formatter.string(from: dateFromString!)

    return stringDate

}

How to convert a sting to a date, and back again, in swift?

2 Answers2