Question

我有两个流，看起来如下：

const source1 = Rx.Observable.of([1,2,3,4,5])
  .map(() => "I am source 1")
  .do((x) => console.log(x));
const sub1 = source1.subscribe((v) => console.log("Subscribe 2"));

const source2 = Rx.Observable.fromEvent(document, 'click')
   .do(() => console.log("execute!"))
   .switchMapTo(source1)
   .do(() => console.log("After switch map."))
   .map((x) => "source2");

source2.subscribe((x) => console.log(x));

如果没有点击文档，我会得到以下输出：

"I am source 1"
"Subscribe 2"

进一步点击输出：

"execute!"
"I am source 1"
"After switch map."
"source2"

如何通过进一步点击强制流source1订阅，并继续使用流source2？

我希望在输出后点击几下后

"I am source 1"
"Subscribe 2"
"execute!"
"I am source 1"
"After switch map."
"source2"

Answer 1

可以将Observable视为函数。订阅就像调用函数一样。

即

const o = Rx.Observable.of(1);
o.subscribe(x => console.log(x));

与

非常相似

const f = () => 1;
console.log ( f() );

就像调用函数一样不会修改函数。订阅Observable不会修改observable。订阅不以任何方式附加到Observable。这是返回的订阅，它持有任何州。

您的示例中的两个订阅调用完全独立，并且与此相同：

const source1 = Rx.Observable.of([1,2,3,4,5])
  .map(() => "I am source 1")
  .do((x) => console.log(x));
const sub1 = source1.subscribe((v) => console.log("Subscribe 2"));

const source1_v2 = Rx.Observable.of([1,2,3,4,5])
  .map(() => "I am the same as source 1")
  .do((x) => console.log(x));

const source2 = Rx.Observable.fromEvent(document, 'click')
   .do(() => console.log("execute!"))
   .switchMapTo(source1_v2)
   .do(() => console.log("After switch map."))
   .map((x) => "source2");

source2.subscribe((x) => console.log(x));

订阅后继续流式传输

1 个答案: