How to configure DateFormatter to capture microseconds

Question

iOS Date() returns date with at least microsecond precision.
I checked this statement by calling Date().timeIntervalSince1970 which results in

Answer 1

Solution by @Vlad Papko has some issue:

For dates like following:

2019-02-01T00:01:54.3684Z

it can make string with extra zero:

2019-02-01T00:01:54.03684Z

Here is fixed solution, it's ugly, but works without issues:

override public func string(from date: Date) -> String {
        dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
        let components = calendar.dateComponents(Set([Calendar.Component.nanosecond]), from: date)

        let nanosecondsInMicrosecond = Double(1000)
        let microseconds = lrint(Double(components.nanosecond!) / nanosecondsInMicrosecond)

        // Subtract nanoseconds from date to ensure string(from: Date) doesn't attempt faulty rounding.
        let updatedDate = calendar.date(byAdding: .nanosecond, value: -(components.nanosecond!), to: date)!
        let dateTimeString = super.string(from: updatedDate)

        let stingWithMicroseconds = "\(date.timeIntervalSinceReferenceDate)"
        let dotIndex = stingWithMicroseconds.lastIndex(of: ".")!
        let hasZero = stingWithMicroseconds[stingWithMicroseconds.index(after: dotIndex)] == "0"
        let format = hasZero ? "%@.%06ldZ" : "%@.%6ldZ"

        let string = String(format: format,
                            dateTimeString,
                            microseconds)

        return string
    }