平面图中的rxjs条件 [英] rxjs condition inside flatmap

问题描述

我想在flatMap中有一个条件来检查第一个可观察者返回的内容.如果不符合条件，我想中断并导航到其他页面.

I want to have a condition inside flatMap that checks what was returned by first observable. If condition is not met I would like to break and navigate to different page.

this.service.getData(id)
  .flatMap((data) => {
    if (!data) {
      return Observable.throw(new NoDataFoundError());
    }
    return Observable.forkJoin(
      this.service.getData2(id2),
      this.service.getData3(id3),
    );
  })
  .subscribe(
    ([data2, data3]) => {
      this.data2= data2;
      this.data3= data3;
    },
    (err) => {
      if (err instanceof NoDataFoundError) {
        this.router.navigate(...);
      }
    }
  );   

目前，我正在抛出特定的错误并捕获该错误，但是我不喜欢这种解决方案，因为它不是唯一可能引发错误并且if无法缩放的代码.

Currently I'm throwing specific error and catching it however I don't like this solution as it's not the only piece of code that could throw an error and the if is not scaling.

我考虑过filter或takeWhile运算符，但无法执行重定向.

I thought about filter or takeWhile operators but I won't be able to execute the redirect.

我还考虑过返回Observable.of而不是抛出它(在第4行中)，但是然后我必须做if in subscription，它也会闻起来.

I also thought about returning Observable.of instead of throwing (in line 4) but then I would have to do the if in subscribe which also smells.

推荐答案

您可以在内执行 this.router.navigate 和 return Observable.empty().flatMap .这样，您将只有一个 if 语句.

You can execute this.router.navigate and return Observable.empty() inside .flatMap. This way you will have a single if statement.

.flatMap(data => {
  if (!data) {
    this.router.navigate(...);
    return Observable.empty();
  }
  return (...);
})

但是通常可观察物应该是懒惰且纯净的(无副作用)，这将使它们可预测且易于编写.副作用应仅由订户执行.

But usually Observables should be lazy and pure(free of side effects) this will make them predictable and easy to compose. Side effects should be performed only by subscriber.

在您的特定情况下，似乎合适的解决方案是将这种逻辑放在路由防护中，如此处所述- https://stackoverflow.com/a/39162538/3772379

In your specific case, it seems like the proper solution would be to put this logic in the route guard, like described here - https://stackoverflow.com/a/39162538/3772379

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