switchMap相关文章
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SwitchMap can cancel in-flight network requests.
先引用rxjs官网对SwitchMap的介绍：
每次emission，之前的inner Observable会被cancel，新的Observable会被subscribe.
可以使用"switch to a new Observable"的方法来帮助记忆switchMap的这一特性。
Typeheads
This works perfectly for scenarios like typeaheads where you are no longer concerned with the response of the previous request when a new input arrives.
This also is a safe option in situations where a long lived inner observable could cause memory leaks, for instance if you used mergeMap with an interval and forgot to properly dispose of inner subscriptions. -
Remember, switchMap maintains only one inner subscription at a time, this can be seen clearly in the first example.
Be careful though, you probably want to avoid switchMap in scenarios where every request needs to complete, think writes to a database. switchMap could cancel a request if the source emits quickly enough. In these scenarios mergeMap is the correct option.
看个例子：
源代码：
ngOnInit(): void { fromEvent(document, 'click') .pipe( // restart counter on every click switchMap(() => interval(1000)) ) .subscribe((oe) => console.log('Jerry: ' + oe)); }
输出：
switchMap的实现：
应用程序调用subscribe：
每次调用intervals函数，内部都会新建一个Observable对象：
调用了当前的next方法后，计数器加一，然后继续在preriod毫秒后，调度下一次执行：
返回一个新的Observable对象：
