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如何收听Firebase更新并触发效果/存储副作用以更新存储状态？

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我对将Firebase与ngrx / store集成非常困惑 . 由于Firebase具有基于套接字的“实时”更新，因此每当我更新Firebase时，商店数据都已与Firebase数据同步 . 问题是，我不知道如何收听Firebase更新并触发带效果/存储的副作用，以便在Firebase和客户端存储上进行更多更新 . 有关如何处理此问题的任何建议 . 现在，我必须使用长拉Observable.interval（5000）策略来触发服务函数来查询Firebase以查明是否发生了更新 . 代码如下：

@Effect() newMessages$ = Observable.interval(5000)
        .withLatestFrom(this.store.select<UiState>("uiState"))
        .map(([any,uiState]) => uiState)
        .debug("We are querying Firebase to see if any update happened...")
        .filter(uiState => Boolean(uiState.userId))
        .switchMap(uiState => this.threadsService.loadNewMessagesForUser(uiState.userId)
          .take(1)
          .switchMap(data => this.threadsService.deleteMessagesQueuePerUser(uiState.userId).mapTo(data))
        )
        .debug("new messages received from server, and deleted temp record from Firebase")
        .withLatestFrom(this.store.select<UiState>("uiState"))
        .map(([unreadMessages, uiState]) => new NewMessagesReceivedAction({
          unreadMessages,
          currentThreadId: uiState.currentThreadId,
          currentUserId: uiState.userId
        }))

loadNewMessagesForUser和deleteMessagesQueuePerUser是firebase AngualrFire2函数 . 它基本上使用list来获取（跟踪）firebase上的新更新，并在我们知道自最近5秒以来发生了什么新更新时删除firebase上的跟踪数据 . 我想删除这个逻辑，只是直接听firebase更新并触发我的副作用 .

angular firebase rxjs ngrx

1 回答

  • 1

    理论上，这应该触发连续更新，并在 uiState 更改时切换到新的更新流 .

    @Effect() newMessages$ = this.store.select<UiState>("uiState")
        .debug("We are querying Firebase to see if any update happened...")
        .filter(uiState => Boolean(uiState.userId))
        .switchMap(uiState => this.threadsService.loadNewMessagesForUser(uiState.userId)
          .do(() => this.threadsService.deleteMessagesQueuePerUser(uiState.userId).subscribe())
          .map(unreadMessages => new NewMessagesReceivedAction({
              unreadMessages,
              currentThreadId: uiState.currentThreadId,
              currentUserId: uiState.userId
            })
          )
        )
        .debug("new messages received from server, and deleted temp record from Firebase");
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