How to format time in "h m s" format in swift using `Duration.TimeFormatStyle`

I wrote an extension of TimeInterval which returns a string in the format "h m s". For example, 5 hours, 33 minutes and 15 seconds would be written as "5h 33m 15s". This is the code:

extension TimeInterval {
  init(hours: Int, minutes: Int, seconds: Int) {
    self = Double(hours * 3600 + minutes * 60 + seconds)
  }

  func toString() -> String {
    let totalSeconds = Int(self)
    let hours = totalSeconds / 3600
    let minutes = (totalSeconds % 3600) / 60
    let seconds = totalSeconds % 60

    if hours >= 1 {
      return "\(hours)h \(minutes)m"
    } else if minutes >= 1 {
      return "\(minutes)m \(seconds)s"
    } else {
      return "\(seconds)s"
    }
  }
}

I'd like to achieve this same functionality using Apple's Duration.TimeFormatStyle fashion. For example,I can do the following:

let style = Duration.TimeFormatStyle(pattern: .hourMinuteSecond)
var formattedTime = Duration.seconds(someInterval).formatted(style)

which I think is better practice than writing a toString() function as an extension of TimeInterval, but I'm not sure how to go about creating this style. Any guidance would be great.

What you are looking for is called Duration UnitsFormatStyle units with narrow width:

let duration: Duration = .seconds(15 + 33 * 60 + 5 * 3600)
let string = duration.formatted(.units(width: .narrow)) // "5h 33m 15s"