用其他 Observable 过滤 RxJava Observable [英] Filter RxJava Observable with other Observable

问题描述

我使用 RxAndroid 2.0.1 和 RxJava 2.0.6.

I'm using RxAndroid 2.0.1 with RxJava 2.0.6.

我有两个可观察对象:一个基于某个字符串 (ID) 返回 Maybe.当返回可选对象时，我必须调用第二个接受 MyObject 实例并在对象满足某些条件时返回 Single 的对象.然后我可以对对象实例做一些进一步的操作.

I have two observables: one returns Maybe<MyObject> based on some String (ID). When the optional object is returned, I have to call the second one that takes the MyObject instance and returns Single<Boolean> if object meets some conditions. Then I can do some further operations with the object instance.

我目前的实现如下:

objectDAO.getById(objectId)
    .subscribe(
        myObject -> checkCondition(myObject),
        throwable -> /* Fallback */,
        () -> /* Fallback */
    );

private void checkCondition(final MyObject myObject) {
  otherDAO.checkCondition(myObject)
    .subscribe(
        isTrue -> {
          if (isTrue) {
            // yay! now I can do what I need with myObject instance
          } else {
            /* Fallback */
          }
        },
        throwable -> /* Fallback */
    );
}

现在我想知道如何简化我的代码.我的想法:

Now I'm wondering how could I simplify my code. My ideas:

1. 尝试使用 zip - 我不能，因为在第一个返回 MyObject 之前无法订阅第二个 Observable

1. Try to use zip - I can't because second Observable can't be subscribed until the first one returns the MyObject

尝试使用 filter - 现在的问题是我需要使用阻塞 get 来调用第二个 observable.它可能会工作，但看起来像代码异味:

Try to use filter - Now the issue is that I need to use blocking get to call second observable. It will propably work, but looks like a code smell:

objectDAO.getById(objectId)
  .filter(myObject ->
    otherDAO.checkCondition(myObject).blockingGet()
  )
  .subscribe(
      myObject -> checkCondition(myObject),
      throwable -> /* Fallback */,
      () -> /* Fallback */
  );

尝试使用 flatMap - 第二个 observable 返回布尔值，而我需要返回原始对象.因此，我需要使用 blockingGet 映射代码片段并返回原始对象或 Maybe.empty()

Try to use flatMap - The second observable returns Boolean while I need to return the original object. Because of that I need to mape a code snippet with blockingGet and return original object or Maybe.empty()

有什么建议可以让代码干净"(它更小，但仍然清楚内部发生的事情)吗?

Any suggestions how to do it in such a way that the code is "clean" (it's smaller and it's still clear what's happening inside)?

推荐答案

你可以做的一件事:

objectDAO.getById(objectId)
    .flatMapSingle(myObject -> otherDAO
        .checkCondition(myObject)
        .map(isTrue -> Pair.create(myObject, isTrue))
    )

然后你有一个 Observable> 并且可以按照你想要的方式继续:subscribe 直接并检查 Boolean 在那里，filter 通过布尔值等

Then you have an Observable<Pair<MyObject, Boolean>> and can proceed however you want: subscribe directly and check the Boolean there, filter by the Boolean value, etc.

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