返回项目和转换结果的flatMap

Question

我有一个不那么漂亮的RxJava流程:-(

)

RxView.clicks(sendButton)
      .flatMap(ignored -> cameraManager.getCamera())
      .flatMap(camera -> camera.isReachable())
      .filter(reachable -> reachable)
      .flatMap(ignored -> cameraManager.getCamera())
      .flatMap(camera -> camera.sendCommand("foo bar"))
      .subscribe(send -> Timber.i("send successful"),
                 error -> Timber.e(error, "send failed: "));

我不喜欢这群cameraManager.getCamera()用相机做点什么。

是否有一种方法可以使flatMap同时返回项目和其转换的结果，如flatMap(camera -> Pair.create(camera, camera.isReachable())) ?

RxView.clicks(sendButton)
      .flatMap(ignored -> cameraManager.getCamera())
      .flatMap(camera -> Pair.create(camera, camera.isReachable()))
      .filter(pair -> pair.second)
      .flatMap(pair -> pair.first.sendCommand("foo bar"))
      .subscribe(send -> Timber.i("send successful"),
                 error -> Timber.e(error, "send failed: "));

更多代码来理解我的代码片段:

private class Bar {
    private CameraManager cameraManager = new CameraManager();
    private View          sendButton    = null;
    public Bar() {
        bind();
    }
    private void bind() {
        RxView.clicks(sendButton)
              .flatMap(ignored -> cameraManager.getCamera())
              .flatMap(camera -> camera.isReachable())
              .filter(reachable -> reachable)
              .flatMap(ignored -> cameraManager.getCamera())
              .flatMap(camera -> camera.sendCommand("foo bar"))
              .subscribe(send -> Timber.i("send successful"),
                         error -> Timber.e(error, "send failed: "));
    }
}
private class CameraManager {
    public Observable<Camera> getCamera() {
        return Observable.just(new Camera());
    }
}
public class Camera {
    private BehaviorSubject<Boolean> reachable = BehaviorSubject.create(false);

    public Observable<Boolean> isReachable() {
        return reachable.asObservable();
    }
    public Observable<Boolean> sendCommand(String msg) {
        return Observable.create(subscriber -> {
            // send message...
            final boolean sendSuccessful = true;
            if (sendSuccessful) {
                subscriber.onNext(true);
                subscriber.onCompleted();
            } else {
                subscriber.onError(new Exception());
            }
        });
    }
}

Answer 1

有一个flatMap过载，它有一个额外的Func2<T, U, R>，它接受原始元素和每个元素生成的Observable<U>，并返回一个要发出的值。

Observable.range(1, 10)
.flatMap(v -> Observable.range(1, 2), (v, w) -> v + 100 * w)
.subscribe(System.out.println);