Question

我有这个史诗：

export const fetchProductsFulfilledEpic = action$ =>
  action$.ofType(FETCH_PRODUCTS_FULFILLED)
    .mergeMap(action => {
      return Observable.of(
        updateSearchResults(action.payload),
        toggleMenu(),
        updateRegion(action.payload)
      ).catch(error => Observable.of(
        fetchProductsRejected(error))
        )
    })

我想只返回

updateSearchResults(action.payload),
toggleMenu(),
updateRegion(action.payload)

如果action.payload.products.length大于0，否则显示警告。

Attmept：

export const fetchProductsFulfilledEpic = action$ =>
  action$.ofType(FETCH_PRODUCTS_FULFILLED)
    .mergeMap(action => {
      Observable.if(() => action.payload.products.length > 0,
        Observable.of(
          updateSearchResults(action.payload),
          toggleMenu(),
          updateRegion(action.payload)
        ), Observable.of(...enter alert observable here...)
      ).catch(error => Observable.of(
        fetchProductsRejected(error))
        )
    })

收到错误：

您提供了“未定义”的预期流。你可以提供一个Observable，Promise，Array或Iterable。

如何返回上面的Observable.of，如果showAlertDialog，则返回action.payload.products.length < 1的观察点。

Answer 1

mergeMap内的正常条件怎么样？

export const fetchProductsFulfilledEpic = action$ =>
  action$.ofType(FETCH_PRODUCTS_FULFILLED)
    .mergeMap(action => {
      if (action.payload.products.length > 0) {
        return Observable.of(
          updateSearchResults(action.payload),
          toggleMenu(),
          updateRegion(action.payload)
        );
      } else {
        return Observable.of(
          showAlertDialog()
        );
      }
    })

作为一个侧面点，您的catch目前无关紧要，因为Observable.of永远不会抛出错误：

.mergeMap(action => {
  return Observable.of(
    updateSearchResults(action.payload),
    toggleMenu(),
    updateRegion(action.payload)
  // this is catching errors on the above Observable but
  // this Observable will never ever throw errors
  ).catch(error => Observable.of(
    fetchProductsRejected(error)
  ))
})

如果有效载荷长度<1，则返回不同的可观察量。 1

1 个答案: