RxJava- 在静态文本中放置几个 Observable 值？

Question

我听几个响应式编程的人说 "don't break the monad, just continue it"。我看到了这其中的优点。我仍然对某些情况感到困惑，尤其是当 Observable 最终被消费或订阅时。当必须同时消耗多个 observable 时，这会更加混乱，并且将它们组合成单个 observable 感觉不太实用。

比方说我有一个 TrackedAircraft 类型。它的一些属性是最终的，而其他属性是 Observable.

public interface TrackedAircraft {

    public int getFlightNumber();
    public int getCapacity();
    public Observable<String> getOrigin();
    public Observable<String> getDestination();
    public Observable<Integer> getMileage();
    public Observable<Point> getLocation();

}

我可以很容易地将其连接到 GUI，只需订阅控件，以便在每个属性的每次发射时进行更新。但是电子邮件或静态文本正文呢？这不是那么简单，因为我能想到的不破坏 monad 的唯一方法是组合所有 observable，这听起来很痛苦，尤其是当我有一个 Observable 发射 TrackedFlights 时。

这种情况可以屏蔽吗？还是有一种我没有想到的更单一的方式来完成这个？

public static String generateEmailReportForFlight(TrackedAircraft flight) { 
    return new StringBuilder().append("FLIGHT NUMBER: ").append(flight.getFlightNumber()).append("\r\n")
    .append("CAPACITY: ").append(flight.getCapacity()).append("\r\n")
    .append("ORIGIN: ").append(flight.getOrigin() /*What do I do here without blocking?*/)
    .append("DESTINATION: ").append(flight.getDestination() /*What do I do here without blocking?*/)
    .append("MILEAGE: ").append(flight.getMileage() /*What do I do here without blocking?*/)
    .append("LOCATION: ").append(flight.getLocation() /*What do I do here without blocking?*/)
    .toString();
}

///

Observable<TrackedAircraft> trackedFlights = ...;
trackedFlights.map(f -> generateEmailReportForFlight(f));

Answer 1

可以使用flatMap + combineLatest:

Observable<TrackedAircraft> trackedFlights = ...

trackedFlights
.flatMap(flight -> emailReport(flight))
.subscribe(msg -> sendEmail(msg));

Observable<String> emailReport(TrackedAircraft flight) {
    return Observable.combineLatest(
        flight.getOrigin(), 
        flight.getDestination(), 
        flight.getMileage(), 
        flight.getLocation()
        (origin, destination, mileage, location) -> {
             return new StringBuilder()
             .append("FLIGHT NUMBER: ").append(flight.getFlightNumber())
             .append("\r\n")
             .append("CAPACITY: ").append(flight.getCapacity())
             .append("\r\n")
             .append("ORIGIN: ").append(origin)
             .append("\r\n")
             .append("DESTINATION: ").append(destination)
             .append("\r\n")
             .append("MILEAGE: ").append(mileage)
             .append("\r\n")
             .append("LOCATION: ").append(location)
             .toString();
        }
    )
}

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