How to format a time interval with the new Foundation formatted method?

Question

I'm trying to use the DateComponentsFormatter with the new Foundation formatters. To format a date, I can do something like this:

Date.now.formatted(.dateTime.hour().minute().second())
// 5:03:17 PM

However, I'm trying to use this new API for using the DateComponentsFormatter:

let duration: TimeInterval = 0

let formatter = DateComponentsFormatter()
formatter.unitsStyle = .positional
formatter.allowedUnits = [.minute, .second]
formatter.zeroFormattingBehavior = [.pad]

let formattedDuration = formatter.string(from: 0)
// 00:00

How can I use the new Foundation formatters API for DateComponentsFormatter to achieve this?

Answer 1

AFAIK the formatted method for a time interval only works with Duration objects which needs to be initialized with a timeval:

let timeInterval: TimeInterval = 125.0
let tmv = timeval(tv_sec: Int(timeInterval), tv_usec: 0)
Duration(tmv)
    .formatted(.time(pattern: .hourMinuteSecond))  // "0:02:05"
Duration(tmv)
    .formatted(.time(pattern: .minuteSecond))      // "2:05"

or

Duration(
    secondsComponent: Int64(timeInterval),
    attosecondsComponent: 0
).formatted(.time(pattern: .minuteSecond))  // "2:05"

You can also use its static methods for initialization:

let timeInterval: TimeInterval = 125.0
var duration: Duration = .seconds(timeInterval)
duration += .milliseconds(789)  // 125.789 seconds
    
duration.formatted(.time(pattern: .minuteSecond))  // "2:06"

And if you need further customization:

duration.formatted(.time(pattern: .minuteSecond(padMinuteToLength: 2)))  // "02:06"
duration.formatted(.time(pattern: .minuteSecond(padMinuteToLength: 2, roundFractionalSeconds: .down)))  // "02:05"
duration.formatted(.time(pattern: .minuteSecond(padMinuteToLength: 2, fractionalSecondsLength: 3)))  // "02:05.789"