小编Ant*_*kov的帖子

我一直在Playground中的中级Swift WWDC会话中关注弱引用示例.我稍微修改了代码如下:

class Apartment {
    let address: Int

    init(address: Int) {
        self.address = address
    }

    weak var tenant: Person?
}

class Person {
    let name: String

    init(name: String){
        self.name = name
    }

    weak var home: Apartment?

    func moveIn(apt: Apartment) {
        self.home = apt
        apt.tenant = self
    }
}

var renters = ["John Appleseed": Person(name: "John Appleseed")]
var apts = [16: Apartment(address: 16)]

renters["John Appleseed"]!.moveIn(apts[16]!)
renters["John Appleseed"] = nil // memory should be released here

// then apts[16].tenant should …

我正在尝试在Async.AwaitObservable开始使用的异步工作流程中使用Fsharpx Async.StartWithContinuations.出于某种原因,如果用于启动此工作流的取消令牌在等待可观察时被取消(但在工作流的其他部分期间不被取消),则永远不会调用取消继续.但是,如果我把它放在一个中use! __ = Async.OnCancel (interruption),那么就会调用中断函数.有人可以澄清为什么会发生这种情况,最好的方法是做什么,并确保其中一个延续函数始终被调用？

open System
open System.Reactive.Linq
open FSharp.Control.Observable
open System.Threading

[<EntryPoint>]
let main _ =
    let cancellationCapability = new CancellationTokenSource()

    let tick = Observable.Interval(TimeSpan.FromSeconds 1.0)
    let test = async {
        let! __ = Async.AwaitObservable tick
        printfn "Got a thing." }

    Async.StartWithContinuations(test,
        (fun () -> printfn "Finished"),
        (fun exn -> printfn "Error!"),
        (fun exn -> printfn "Canceled!"),
        cancellationCapability.Token)

    Thread.Sleep 100
    printfn "Cancelling..."
    cancellationCapability.Cancel()

    Console.ReadLine() |> ignore
    0 // return an integer exit …