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我怎么能让一个redux可观察的史诗只有在另一个史诗没有运行时才能继续

redux-observable rxjs javascript

0

Josh Mc · 技术社区 · 6 年前

我基本上是在寻找史诗:

Epic B-当请求_B进入时,如果Epic A没有启动继续,否则等待Epic_A_END完成。

感觉我需要一个计数器来增加EPIC_a_启动时的增量和EPIC_a_完成时的递减,但我不确定如何继续。

如果我们能有一个类似psuedo代码的操作员就好了:

// Operator we are trying to write
const waitForActionsToComplete = (startAction, endAction) => {
   // Not sure how to structure this so that it waits for there to be equal of both actions passing through
}


// Epic A
const EPIC_A_FILTER = (action$, state$) =>
  action$.pipe(
    of(actions.REQUEST_A),
    waitForActionsToComplete(actions.EPIC_B_START, actions.EPIC_B_END),
    mergeMap(() => { type: actions.EPIC_A_START }));

const EPIC_A_PROCESS = (action$, state$) =>
  action$.pipe(
    of(actions.EPIC_A_START),
    ...async task,
    mergeMap(() => { type: actions.EPIC_A_END }));


// Epic B
const EPIC_B_FILTER = (action$, state$) =>
  action$.pipe(
    of(actions.REQUEST_B),
    waitForActionsToComplete(actions.EPIC_A_START, actions.EPIC_A_END),
    mergeMap(() => { type: actions.EPIC_B_START }));

const EPIC_B_PROCESS = (action$, state$) =>
  action$.pipe(
    of(actions.EPIC_B_START),
    ...async task,
    mergeMap(() => { type: actions.EPIC_B_END }));

0 回复 | 直到 6 年前

1

0

NickL 6 年前

你可以利用 scan

action$.pipe(
    of(actions.REQUEST_A, actions.REQUEST_B, actions.EPIC_A_END, actions.EPIC_B_END),
    scan(({queue}, current) => {
      if (current is epic end action)
        if (queue is not empty) {
          return { queue: queue.slice(1), triggerEpic: EPIC_A_START or EPIC_B_START depending on queue[0]  }
        }
        else {
          return { queue, triggerEpic: null };
        }
      }
      else {
        if (queue is not empty) {     
          return { queue: [...queue, current], triggerEpic: null };
        }
        else {
          return { queue: [], triggerEpic: EPIC_A_START or EPIC_B_START depending on current }; 
        } 
      } 
    }, { queue: [], triggerEpic: null }),
    filter(x => x.triggerEpic !== null),
    map(x => x.triggerEpic)
)