Flowable.fromPublisher 需要一个 Publisher，那它为什么要接受一个 Subscriber？

Question

方法签名是：

public static <T> Flowable<T> fromPublisher(Publisher<? extends T> source) {...}

但如果我编写这段代码，它会以某种方式工作：

Flowable<String> flowable = Flowable.fromPublisher(subscriber -> {
  subscriber.onNext("But onNext belongs in a subscriber...");
  subscriber.onNext("Which means I am passing a subscriber instead of a publisher");
  subscriber.onNext("What's happening?");
  subscriber.onComplete();
});

我知道我没有正确看待这个问题。有人可以解释传递 Subscriber 而不是 Publisher 的工作原理吗？

Answer 1

这一点：

subscriber -> {
  subscriber.onNext("But onNext belongs in a subscriber...");
  subscriber.onNext("Which means I am passing a subscriber instead of a publisher");
  subscriber.onNext("What's happening?");
  subscriber.onComplete();
}

是一个 lambda 表达式，是 Publisher 的一个实现。您的代码等效于以下代码（使用匿名类）：

Flowable<String> flowable = Flowable.fromPublisher(new Publisher<String>() {
  @Override
  public void subscribe(Subscriber<? super String> subscriber) {
    subscriber.onNext("But onNext belongs in a subscriber...");
    subscriber.onNext("Which means I am passing a subscriber instead of a publisher");
    subscriber.onNext("What's happening?");
    subscriber.onComplete();
  }
});