How to format the Duration object in Swift - swift

Question

Swift released a new Duration object that is "a representation of high precision time."
I'm using it like this:
let clock = ContinuousClock()
let duration = clock.measure {
// Code or function call to measure here
}
print("Duration: \(duration)")
If the duration really short it prints out something like this:
8.2584e-05 seconds
Instead of scientific notation, I would like to always display as seconds: 0.000082584 seconds
Does anyone know how to always keep the format in seconds?

Answer 1

Just like Dates, Durations support the formatted method. You can give it either the TimeFormatStyle (time) or UnitsFormatStyle (units). For your desired format, it looks like the latter is more suitable. You basically want a fractionalPart that has a very large allowed length.
Though from my experiments, it still rounds everything to nanosecond-precision, even though Duration can support higher precisions. This is perhaps because nanoseconds is the smallest supported unit in Duration.UnitsFormatStyle.Unit.
For example:
let duration: Duration = .nanoseconds(1234)
print(
duration.formatted(.units(
width: .wide,
fractionalPart: .init(lengthLimits: 1...1000)
))
)
Output:
0.000001234 seconds
By default, this will also include hours and minutes if the duration is long enough. If you don't want that, pass allowed: [.seconds] as the first parameter:
duration.formatted(.units(
allowed: [.seconds],
width: .wide,
fractionalPart: .init(lengthLimits: 1...1000)
))