ISO8601DateFormatter 不将字符串转换为日期

Question

I have this datetime string 2020-03-09T11:53:39.474Z . I need to convert it to a Date

let dateString = "2020-03-09T11:53:39.474Z"
if let date = ISO8601DateFormatter().date(from: dateString) {
    print(dateFormatter.string(from: date))
} else {
    print("Could not convert date")
}

But it fails to convert it properly.

Any idea why this it's happening?

Answer 1

The designated initialiser init() of ISO8601DateFormatter does this:

By default, a formatter is initialized to use the GMT time zone, the RFC 3339 standard format ("yyyy-MM-dd'T'HH:mm:ssZZZZZ"), and the following options: withInternetDateTime , withDashSeparatorInDate , withColonSeparatorInTime , and withTimeZone .

Obviously, your date is not in the format yyyy-MM-dd'T'HH:mm:ssZZZZZ , because it has a milliseconds component.

You just need to add the withFractionalSeconds option:

let dateString = "2020-03-09T11:53:39.474Z"
let formatter = ISO8601DateFormatter()
formatter.formatOptions = [
    .withInternetDateTime, 
    .withFractionalSeconds, 
    .withColonSeparatorInTime, 
    .withDashSeparatorInDate, 
    .withTimeZone]
if let date = formatter.date(from: dateString) {
    print(date)
} else {
    print("Could not convert date")
}

I personally like to list the options all out to make the code clearer, but you can also do:

formatter.formatOptions.insert(.withFractionalSeconds)