65日目

structured concurrency

concurrentに走るTaskが構造化されているからstructured concurrencyと呼ぶらしい．

import Foundation
import _Concurrency

struct Photo {}

func downloadPhoto(named: String) async -> Photo {
    await Task.sleep(2 * 1_000_000_000)
    return Photo()
}

Task {
    // unstructured concurrency
    let handle =
    // structured concurrency
    Task { // parent task
        await withTaskGroup(of: Photo.self) { taskGroup in
            let photoNames = ["a", "b"]
            for name in photoNames {
                taskGroup.addTask { // child task
                    return await downloadPhoto(named: name)
                }
            }
        }
    }
    // structured concurrency

    _ = await handle.result
    // unstructured concurrency
}

昨日書いた邪悪な例はこれで善良にかけそうな気がしたけどいま揚げ物していて焦げそうなので明日考える．