继续使用订阅异常后 [英] Continue using subscription after exception

问题描述

我在尝试一种类型，以搜索反应，扩展的样品，它接受一个字符串从一个文本框（如果它的事项WPF应用程序），并做了潜在的冗长的服务器端搜索（模拟在我的情况与Thread.sleep代码），并将结果显示在列表框（S）。

I was trying out a "type-to-search" Reactive-Extensions sample which takes a string from a textbox (WPF app if it matters) and does a potentially-lengthy server-side search (simulated in my case with a Thread.Sleep) and displays the result(s) in a listbox.

这个特殊的模块的主要特点是：

The key features of this particular "module" would be :

• 在异步检索;而搜索UI不冻结
• 在节流;快速打字也不会产生一个服务器端的搜索每次击键
• 在不同的搜索;经过搜索房间隔缺损，并有结果（S）显示的打字速度快后退键，D（即删除最后一个字符，快速重新键入）将不会重新服务器端的搜索
• 落中间，结果;如果我输入房间隔缺损，并简要等待（导致服务器端的搜索即将推出），然后之前，结果ASD显示完成搜索字符串的中介/特殊结果被丢弃

<强>的问题是，从重方法的单个异常（一个做服务器端搜索'）订阅被终止，并且不能使用后

到目前为止，我只找到了一个解决办法通过resubscriping到的IObservable对象，但这种感觉是错误的。我也曾尝试.Retry（），但虽然我得到重用订阅我的的OnError 处理程序不会被再调用。

So far I only found out a workaround by resubscriping to the IObservable object but this feels wrong. I have also tried .Retry() but although I get to reuse the subscription my OnError handler does not get called anymore.

在code是这样的：

    private IObservable<object> _resultsFromTypeToSearch;

    private void SetupObserver()
    {
        var throttledUserInput =
            (from evt in Observable.FromEventPattern<TextChangedEventArgs>(TxtSearch, "TextChanged")
             select ((TextBox)evt.Sender).Text)
                .Throttle(TimeSpan.FromSeconds(0.6)) // this ensures that only after 0.6 seconds the user input is taken into consideration
                .DistinctUntilChanged();             // this ensures only changed input is taken into consideration

        var getDataFunc = new Func<string, object>(GetExpensiveData);
        var searchAsync = Observable.FromAsyncPattern<string, object>(getDataFunc.BeginInvoke, getDataFunc.EndInvoke);

        var z = from text in throttledUserInput
                from word in searchAsync(text).TakeUntil(throttledUserInput)
                select word;  // TakeUntil will drop an ongoing search if a new search is requested in the meantime
        _resultsFromTypeToSearch = z.ObserveOn(TxtSearch); // this ensures that we'll get notified on the UI thread
        _resultsFromTypeToSearch.Subscribe(PresentResults, OnError);
    }

    private void OnError(Exception obj)
    {
        ClearUI();
        MessageBox.Show("Error");

        _resultsFromTypeToSearch.Subscribe(PresentResults, OnError); // THIS IS MY WORKAROUND WHICH FEELS BAD
    }

    private void ClearUI()
    {
        IsBusy = false;
        Results.Clear();
    }

    private void PresentResults(object result)
    {
        ClearUI();
        Results.Add(result.ToString());
    }

    private object GetExpensiveData(string searchString)
    {
        IsBusy = true;
        if (DateTime.Now.Millisecond % 3 == 0) throw new ServerException();
        Thread.Sleep(2000);
        return "Data for " + searchString;
    }

什么更好的办法来做到这一点？

推荐答案

我被误解接收。序列一旦它出现故障，不能重复使用。简单的解决方案是重新创建订阅（S），即：再次调用SetupObserver（）

I was misunderstanding Rx. A sequence once it gets faulted it can not be reused. The simple solution is to recreate the subscription(s), i.e.: call again SetupObserver()

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