Issue
How do I use the new Swift 5.5 await keyword to wait for a duration of time?
Normally, with completion handlers, you would have something like this by using DispatchQueue's asyncAfter(deadline:execute:):
func someLongTask(completion: @escaping (Int) -> Void) {
DispatchQueue.global().asyncAfter(deadline: .now() + 1) {
completion(Int.random(in: 1 ... 6))
}
}
someLongTask { diceRoll in
print(diceRoll)
}
How can this be converted to using async & await in Swift 5.5?
Solution
iOS 16+ / macOS 13+
There's a newer API, sleep(until:tolerance:clock:), used like so:
// 3 seconds
try await Task.sleep(until: .now + .seconds(3), clock: .continuous)
iOS <16 / macOS <13
You can use Task.sleep(nanoseconds:) to wait for a specific duration. This is measured in nanoseconds, not seconds.
Here's an example:
func someLongTask() async -> Int {
try? await Task.sleep(nanoseconds: 1 * 1_000_000_000) // 1 second
return Int.random(in: 1 ... 6)
}
Task {
let diceRoll = await someLongTask()
print(diceRoll)
}
It may be easier to use an extension for sleep so you can just pass in seconds:
extension Task where Success == Never, Failure == Never {
static func sleep(seconds: Double) async throws {
let duration = UInt64(seconds * 1_000_000_000)
try await Task.sleep(nanoseconds: duration)
}
}
Which would now be called like so:
try await Task.sleep(seconds: 1)
Note that sleep is called with try. An error is thrown if the sleep is cancelled. If you don’t care if it’s cancelled, just try? is fine.
Answered By - George Answer Checked By - Gilberto Lyons (PHPFixing Admin)
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