Swift 异步等待不会在项目中触发，但在 Xcode playground 中工作正常

发布于06月13日

下面的代码段在Xcode playground中工作，但如果我在项目中投入.onAppear/.task，则无法工作.

如果有人能帮我，我将不胜感激.

let n = Notification.Name("event")
Task {
    for await value in NotificationCenter.default.notifications(named: n, object: nil) {
        if let str = value.object as? String {
            await asyncPrint(value: str)
        }
    }
}

NotificationCenter.default.post(name: n, object: "event1")
NotificationCenter.default.post(name: n, object: "event2")
NotificationCenter.default.post(name: n, object: "event3")

推荐答案

如果在Task之外、post之前创建通知流，则可以消除此计时问题:

let n = Notification.Name("event")
let notifications = NotificationCenter.default.notifications(named: n, object: nil)

Task {
    for await notification in notifications {
        if let string = notification.object as? String {
            await asyncPrint(value: string)
        }
    }
}

NotificationCenter.default.post(name: n, object: "event1")
NotificationCenter.default.post(name: n, object: "event2")
NotificationCenter.default.post(name: n, object: "event3")