为什么不是 Observable.Finally 被调用?

问题描述

我不理解Finally 方法.在这种情况下它不会触发.

I'm not understanding the Finally method. It doesn't fire in this situation.

[TestMethod]
public void FinallyHappensOnError()
{
    bool finallyActionHappened = false;
    try
    {
        Observable
        .Throw<Unit>(new DivideByZeroException())
        .Finally(() => finallyActionHappened = true)
        .Subscribe();
    }
    catch
    {
    }
    Assert.IsTrue(finallyActionHappened);
}

这个使用 Do 而不是 finally 来工作.我不明白为什么它适用于 Do 而不是最终.

This one works using Do rather than Finally. I don't understand why it works with Do but not Finally.

[TestMethod]
public void CanRecordWhenSequenceFinishes()
{
    bool sequenceFinished = false;
    try
    {
        Observable.Throw<Unit>(new DivideByZeroException())
        .Do(
            onError: ex => { sequenceFinished = true; },
            onCompleted: () => sequenceFinished = true,
            onNext: _ => { })
        .Subscribe();
    }
    catch
    {

    }
    Assert.IsTrue(sequenceFinished);
}

推荐答案

你的代码(双向)是一个竞争条件.竞争条件用 .Do 解决正确的方法，用 .Finally 解决错误的方法.为什么比如何避免它更不重要:

Your code (both ways) is a race condition. The race condition resolves the right way with .Do and the wrong way with .Finally. Why is less relevant than how to avoid it:

public async Task FinallyHappensOnError()
{
    bool finallyActionHappened = false;
    try
    {
        await Observable.Throw<Unit>(new DivideByZeroException())
            .Finally(() => finallyActionHappened = true);
    }
    catch
    {
    }
    Assert.IsTrue(finallyActionHappened);

}

或者，如果您不想使用 TPL/async/await:

or, if you don't want to use TPL/async/await:

[TestMethod]
public void FinallyHappensOnError()
{
    bool finallyActionHappened = false;
    try
    {
        Observable
        .Throw<Unit>(new DivideByZeroException())
        .Finally(() => finallyActionHappened = true)
        .Subscribe(
            _ => {},
            () => Assert.IsTrue(finallyActionHappened)
        );
    }
    catch
    {
    }

}

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