Question

试图让一个事件用初始事件数据触发多个switchMap。

每个动作都会创建对某些转换的承诺，然后将其写入文件系统。这些动作是独立且无关的，但是使用相同的数据只是出于不同的目的，因此不应将其合并。

当前使用水龙头而不是switchMap，这可能导致多个事件同时运行。

const SomeApiCall = () => {return {some: 'data'} }
const AllowsDoAction = () => {console.log('Parsing API and writting some things to FS -- PLACEHOLDER')}
const SomeTimeDoThisActionTo = () => {console.log('Parsing API and writting some other things to fs, by asking more data from the API and first, so it is long thing to do, so a new event can arrive first -- PLACEHOLDER')}
const deepEqual = (prev, cur) => prev === cur // normally a proper deepEqual...
const taps = [tap(AllowsDoAction)];
if (someCondition) taps.push(SomeTimeDoThisActionTo)
const observable = timer(0, 500).pipe(
   exhaustMap(SomeApiCall),
   distinctUntilChanged((prev, cur) => deepEqual(prev, cur))
   ...taps
);

Answer 1

我将返回文件系统写入 observables（编辑2）

const SomeApiCall = () => {
  return of({ some: 'data' });
};
const AllowsDoAction = () => {
  console.log('Parsing API and writting some things to FS -- PLACEHOLDER');
  return timer(100).pipe(map(() => 'write 1 finished'));
};
const SomeTimeDoThisActionTo = () => {
  console.log(
    'Parsing API and writting some other things to fs, by asking more data from the API and first, so it is long thing to do, so a new event can arrive first -- PLACEHOLDER'
  );
  return timer(1000).pipe(map(() => 'write 2 finished'));
};

然后使用concatMap等待所有文件系统操作完成。

const deepEqual = (prev, cur) => prev === cur; // normally a proper deepEqual...
const taps = [(AllowsDoAction)];
const someCondition = true;
if (someCondition) {
  taps.push(SomeTimeDoThisActionTo);
}
const reduxStorageEvent$ = of('replace this with real event');

const observable = merge(timer(0, 500), reduxStorageEvent$).pipe(
  exhaustMap(SomeApiCall),
  distinctUntilChanged((prev, cur) => deepEqual(prev, cur)),
  // use switchMap to cancel previous writes (edit 2) 
  // await latest write operations, before starting new writes
  concatMap((someData) => {
    const writes = taps.map((tapFx) => {
        return tapFx(someData);
    });
    // wait for all writes
    return forkJoin(...writes);
  })
);

concatMap就像一个队列。此队列中的第一个必须先完成，然后才能开始。

对单个事件进行多项操作

1 个答案: