Question

我是Rx的新手所以请耐心等待。

我想在Task<T>中包含IObservable<T>。到目前为止一切顺利：

Task<T> task = Task.Factory.StartNew(...);
IObservable<T> obs = task.ToObservable();

现在，我想要的是在观察者取消订阅时发出取消信号：

var cancel = new CancellationToken();
Task<T> task = Task.Factory.StartNew(..., cancel);

IObservable<T> obs = task.ToObservable(); //there should be a way to tie the cancel token
                                          //to the IObservable (?)

IDisposable disposable = obs.Subscribe(...);
Thread.Sleep(1000);
disposable.Dispose(); // this should signal the task to cancel

我该怎么做？

FWIW这里是生成此切线的场景：Rx and tasks - cancel running task when new task is spawned?

Answer 1

这是我能想到的最简单的方法，使用Observable.Create：

static IObservable<int> SomeRxWork()
{
    return Observable.Create<int>(o =>
    {
        CancellationTokenSource cts = new CancellationTokenSource();
        IDisposable sub = SomeAsyncWork(cts.Token).ToObservable().Subscribe(o);
        return new CompositeDisposable(sub, new CancellationDisposable(cts));
    });
}

static Task<int> SomeAsyncWork(CancellationToken token);

我在评论中暗示的最初方式实际上相当冗长：

static IObservable<int> SomeRxWork()
{
    return Observable.Create<int>(async (o, token) =>
    {
        try
        {
            o.OnNext(await SomeAsyncWork(token));
            o.OnCompleted();
        }
        catch (OperationCanceledException)
        {
        }
        catch (Exception ex)
        {
            o.OnError(ex);
        }
    });
}

Answer 2

假设您有这样的方法：

Task<Gizmo> GetGizmoAsync(int id, CancellationToken cancellationToken);

您可以将其转换为IObservable<Gizmo>，其中订阅会启动Task<Gizmo>，取消订阅会使用以下内容取消订阅。

IObservable<Gizmo> observable = Observable.FromAsync(
    cancellationToken => GetGizmoAsync(7, cancellationToken));

// Starts the task:
IDisposable subscription = observable.Subscribe(...);

// Cancels the task if it is still running:
subscription.Dispose();

Rx - 如何从Task <t>创建IObservable <t>，以便取消订阅取消任务？</t> </t>

2 个答案: