Question

我正在寻找可以过滤我的可观察对象的现有运算符，如果为真，则可观察对象将完成。

我可以这样做：

obs$.pipe(
  filter(value => value),
  first()
);

但是我想知道是否有一种方法可以将filter和first运算符组合在一起。

我认为skipUntil是一个不错的选择，但是它会跳过直到发出 observable 为止，直到传递了真实值为止。

Answer 1

Looks like I had to pay more attention to the docs of first, which does exactly what I was looking for.

// RxJS v6+
import { from } from 'rxjs';
import { first } from 'rxjs/operators';

const source = from([1, 2, 3, 4, 5]);

//emit first item to pass test
const example = source.pipe(first(num => num === 5));

//output: "First to pass test: 5"
const subscribe = example.subscribe(val =>
  console.log(`First to pass test: ${val}`)
);

Answer 2

Use the takeWhile operator:

const $observableThatCompletes = obs$.takeWhile((value) => true !== value);

The resulting observable will complete as soon as value is true.

You can use !value instead of true !== value if you want to match all 'truthy' values.

RxJS-提供的表达式为true时的完整观察

2 个答案: