如何在 Swift Joint Sink 收到至少一个值后停止存储 AnyCancellable？

Question

我有一个接收器，需要在收到第一个值后立即取消。我不关心未来的值，只关心第一个发布的值。因为如果不存储AnyCancelable由接收器创建的，垃圾收集器将删除该接收器，所以我必须存储它。同时，我也必须在sink完成后清理它，否则，我会出现内存泄漏。

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我使用 UUID \xe2\x86\x92 AnyCancelable 映射构建了一个，但我担心这比应有的更复杂；还有另一种方法可以做到这一点吗？联合有什么推荐的？

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@Published var locationState: (location: CLLocation?, error: Error?)?\nvar requestLocationSinks: [String: AnyCancellable] = [:]\n\n// 1. Generate ID to uniquely identify the current sink.\nlet sinkID = UUID().uuidString\n\n// 2. Start the sink and store it in our ID \xe2\x86\x92 AnyCancellable dictionary.\nrequestLocationSinks[sinkID] = $locationState.sink { locationState in\n    if let locationState = locationState {\n        invokeCallbackWithLocationState(locationState)\n    }\n    // 3. Remove the stored AnyCancellable as soon as we received our first value!\n    self.requestLocationSinks.removeValue(forKey: sinkID)\n}\n

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Answer 1

如果您只需要保持它的活动状态直到接收器被调用一次，您可以创建一个临时变量

var cancellable: AnyCancellable?
cancellable = $locationState.sink { locationState in
    if let locationState = locationState {
        invokeCallbackWithLocationState(locationState)
    }
    cancellable = nil
}

这将保留AnyCancellable足够长的时间（因为闭包保留了引用）