Question

是否有一种安全的方法可以推迟创建Observable<T>，但是在创建缓存之前，它必须再次创建它？

Observable.cachedDefer(() -> createExpensiveFiniteObservable().cache(), 5, TimeUnit.MINUTES);

我有构建成本高昂的数据集，我希望它们的缓存时间足以支持进程，但让它们在每次运行之间大致到期。

Answer 1

我已将此功能添加到 rxjava-extras 。下面的代码取决于 rxjava-extras 0.6.8-RC2或更高版本（在Maven Central上）。

运行下面的main方法，您会看到这些结果似乎与您想要的行为相匹配（每当下次订阅的时间间隔为＆gt; = 5秒时重置缓存）：

source emits Tue Oct 13 21:00:16 AEDT 2015
Tue Oct 13 21:00:16 AEDT 2015
Tue Oct 13 21:00:16 AEDT 2015
Tue Oct 13 21:00:16 AEDT 2015
Tue Oct 13 21:00:16 AEDT 2015
Tue Oct 13 21:00:16 AEDT 2015
source emits Tue Oct 13 21:00:31 AEDT 2015
Tue Oct 13 21:00:31 AEDT 2015
Tue Oct 13 21:00:31 AEDT 2015
Tue Oct 13 21:00:31 AEDT 2015
Tue Oct 13 21:00:31 AEDT 2015
Tue Oct 13 21:00:31 AEDT 2015
source emits Tue Oct 13 21:00:46 AEDT 2015
Tue Oct 13 21:00:46 AEDT 2015
Tue Oct 13 21:00:46 AEDT 2015
...

主要方法：

public static void main(String[] args) throws InterruptedException {
    Observable<Date> source = Observable
      .defer(() -> 
         Observable
           .just(new Date())
           .doOnNext(
              d -> System.out.println("source emits " + d)));

    CloseableObservableWithReset<Date> cached = 
        Obs.cache(source, 5, TimeUnit.SECONDS, Schedulers.computation());
    Observable<Date> o = cached
        .observable()
        .doOnSubscribe(() -> cached.reset());
    for (int i = 0; i < 30; i++) {
        o.doOnNext(System.out::println).subscribe();
        Thread.sleep((i % 5 + 1)*1000);
    }
    cached.close();
}

请注意，要重置每个发射的缓存以及您看到的位置

.doOnSubscribe(() -> cached.reset())

把

.doOnSubscribe(() -> cached.reset())
.doOnNext(x -> cached.reset())

RxJava：是否有Observable.cachedDefer（）运算符或某些等价运算符？

1 个答案: