RxJava：等待另一个可观察的结果

Question

如何在转换当前结果的同时等待另一个可观察结果？

我有一个用户 ID 列表 (userIdsList)，我应该将它们转换为地图。 map中key用userId表示，value为boolean，表示userId是否包含在regUsers.

return Observable
   .<List<Long>>from(userIdsList)
   .groupBy(id -> id, id -> regUsers.contains(id)); //PROBLEM: regUsers is Observable<List<Long>>

Answer 1

有点复杂的解决方案。

      List<Long> ids = Arrays.asList(1L, 2L, 3L);
      Observable<List<Long>> regUsers = Observable.just(Arrays.asList(1L, 2L)).cache();

      Observable<Long> idsStream = Observable.from(ids).cache();
      Observable<Boolean> containsStream = idsStream
             .concatMap(id -> regUsers.map(regList -> regList.contains(id)));

      idsStream.zipWith(containsStream, (Func2<Long, Boolean, Pair>) Pair::new)
            .toMap(Pair::getLeft, Pair::getRight).subscribe(System.out::println);


  private static class Pair<K, V> {

    private final K left;
    private final V right;

    public Pair(K left, V right) {
        this.left = left;
        this.right = right;
    }

    public K getLeft() {
        return left;
    }

    public V getRight() {
        return right;
    }
}

RxJava：等待另一个可观察的结果

RxJava: wait another observable result

java

reactive-programming

system.reactive

rx-java