Availability
Technology
init(_ elementType: Element.Type = Element.self, bufferingPolicy limit: AsyncThrowingStream <Element, Failure>.Continuation.BufferingPolicy = .unbounded, _ build: (AsyncThrowingStream <Element, Failure>.Continuation) -> Void) where Failure == ErrorelementTypeThe type of element the Async produces.
limitThe maximum number of elements to hold in the buffer. By default, this value is unlimited. Use a Continuation to buffer a specified number of oldest or newest elements.
buildA custom closure that yields values to the Async. This closure receives an Async instance that it uses to provide elements to the stream and terminate the stream when finished.
The Async received by the build closure is appopriate for use in concurrent contexts. It is thread safe to send and finish; all calls are to the continuation are serialized. However, calling this from multiple concurrent contexts could result in out-of-order delivery.
The following example shows an Async created with this initializer that produces 100 random numbers on a one-second interval, calling yield(_:) to deliver each element to the awaiting call point. When the for loop exits and the stream finishes by calling the continuation’s finish() method. If the random number is divisble by 5 with no remainder, the stream throws a My.
let stream = AsyncThrowingStream<Int, Error>(Int.self,
bufferingPolicy: .bufferingNewest(5)) { continuation in
Task.detached {
for _ in 0..<100 {
await Task.sleep(1 * 1_000_000_000)
let random = Int.random(in: 1...10)
if (random % 5 == 0) {
continuation.finish(throwing: MyRandomNumberError())
return
} else {
continuation.yield(random)
}
}
continuation.finish()
}
}
// Call point:
do {
for try await random in stream {
print ("\(random)")
}
} catch {
print ("\(error)")
}enum AsyncThrowingStream.Continuation.BufferingPolicy struct AsyncThrowingStream.Continuation