我试图在第一个史诗中映射多个动作,在第二个史诗中处理它们,然后在第一个史诗中调用一个回调。
这是我看到的流程:
const fetchMultipleOperationsEpic = action$ => action$.pipe(
ofType(OPERATIONS_FETCH_ALL),
switchMap(({ payload }) => {
const stream = of(...payload.ids.map(processId => fetchOperations({ processId })));
// PROBLEM HERE: 'done' is logged before actions from fetchOperationsEpic complete
return stream.pipe(finalize(() => console.log('done')))
})
)
const fetchOperationsEpic = action$ => action$.pipe(
ofType(OPERATIONS_FETCH),
mergeMap(({ payload }) => fetchOperationData(payload.processId))
)
const fetchOperationData = processId => {
api.fetchOperationsByProcess(processId).pipe(
mergeMap(operations => of(fetchSuccess(), fooAction(), barAction())),
catchError(error => of(fetchOperationsFailure({ processId, error })))
)
}
也尝试使用forkJoin但没有成功:
const fetchMultipleOperationsEpic = action$ => action$.pipe(
ofType(OPERATIONS_FETCH_ALL),
switchMap(({ payload }) => {
const observables = [...payload.ids.map(processId => of(fetchOperations({ processId })))];
// Doesn't wait as well
return forkJoin(observables).pipe(
mergeMap(o => o),
finalize(() => console.log('done'))
)
})
)
实际上,我使其工作的唯一方法是避免调用fetchOperations操作(从而避免调用fetchOperationsEpic),并直接调用fetchOperationData:
const fetchMultipleOperationsEpic = action$ => action$.pipe(
ofType(OPERATIONS_FETCH_ALL),
mergeMap(({ payload }) => {
const observables = [...payload.ids.map(id => fetchOperationData(id))];
return merge(...observables)
.pipe(finalize(() => console.log('done')))
})
)
哪个好。我只是想知道我的初步方法是否真的可行。
你认为你有“问题”的地方:
return stream.pipe(finalize(() => console.log('done')))
这实际上是正确的行为。 finalize
将在其正上方的of
返回的操作列表被发送到商店后立即运行。那是因为你已经明确地将finalize
链接到那个内部可观察者。
您正在考虑的方法的问题是,一旦某个操作进入商店,它就不再属于该特定可观察范围。你不能简单地等待处理其他史诗中的特定动作,因为最终,史诗永远不会真正结束。在严格的RxJS意义上,可观察者从不发出完整的通知。
一般来说,我建议寻找一个使用单个史诗的解决方案(可能与你上一个例子一致)。这允许您简单地链接运算符,例如finalize
,而无需跳过太多的箍。您仍然可以重构您的代码,以便史诗可以使用可重用的函数,以防您想要在不同的史诗之间共享/复制业务逻辑。
您还可以查看依赖于通过不同操作进行史诗间通信的解决方案。但是,根据工作流程的复杂程度,这可能会变得棘手。您需要每个操作来唯一标识子流程。这是一个想法:
const fetchMultipleOperationsEpic = action$ => action$.pipe(
ofType(OPERATIONS_FETCH_ALL),
switchMap(({ payload }) =>
merge(...payload.ids.map(processId =>
concat(
of(fetchOperations({ processId })),
// Note: This keeps the observable running until either
// the corresponding "success" or "failure" action is
// dispatched:
action$.pipe(
filter(action => (action.type === FETCH_SUCCESS || action.type === FETCH_FAILURE) && action.payload.processId === processId),
first(),
ignoreElements(),
),
)
)).pipe(
finalize(() => console.log('done')),
)
)
)
const fetchOperationsEpic = action$ => action$.pipe(
ofType(OPERATIONS_FETCH),
mergeMap(({ payload }) => fetchOperationData(payload.processId))
)
const fetchOperationData = processId => {
api.fetchOperationsByProcess(processId).pipe(
// Note: We have to pass along the `processId` in the
// "success" action so that the inner observables in
// `fetchMultipleOperationsEpic` can complete:
mergeMap(operations => of(fetchSuccess({ processId }), fooAction(), barAction())),
catchError(error => of(fetchOperationsFailure({ processId, error })))
)
}