Unlike mergeMap and switchMap, concatMap focuses on when "inner" subscriptions "complete" by using a "buffer". Each time concatMap receives a value, it adds each value to a "buffer", waits for previous "inner&q…

switchMap is mergeMap that checks for an "inner" subscription. If the "inner" subscription exists, switchMap unsubscribes from that "inner" subscription which effectively "cancels" any pending pushes. import { fromE…

Understanding sources and subscribers makes it much easier to understand what's going on with mergeMap under the hood. Where a typical operator invokes destination.next directly, mergeMap wraps destination.next inside of a new source/subscriber combo…

"the user operation is waiting for building workspace" to complete", 解决办法: 1.选择菜单栏的“Project”,然后把菜单栏中“Build Automatically”前面的对钩去掉. 2.当你修改或添加代码后,选择菜单栏的“Project”,然后选择菜单栏中“Build All”就可以再次编译了.…

Problem Description: ====================  You are attempting to shut down the database and the database hangs.  The alert log contains the following message:      SHUTDOWN: Waiting for active calls to complete   There are no other error messages in…

有时候在关闭数据库时,发出shutdown immediate;命令后一直未关闭.查看ALERT日志.在等待一段时间后日志中有提示: SHUTDOWN: waiting for active calls to complete. 原因是有些进程无法被PMON进程清理.导致SHUTDOWN时无法关闭而HANG住. ==>依据观察,在ORACLE10G及以上版本号.会是例如以下提示:(2015/11/24最新验证ORACLE9206中也会提示进程号) Active call for process…

Like switchMap and mergeMap, concatMap is a shortcut for map() followed by a concatAll(). In this lesson we will explore this RxJS operator and its properties. const clickObservable = Rx.Observable .fromEvent(document, 'click'); function performReque…

While it's great to use the RxJS built-in operators, it's also important to realize you now have the knowledge to write them by yourself if needed. The mapoperator turns out to be a simple MapSubscriber which takes a function and applies it to the va…

Eventually you will feel the need for pausing the observation of an Observable and resuming it later. In this lesson we will learn about use cases where pausing is possible, and what to do when pausing is impossible. const resume$ = new Rx.Subject();…

Instead of writing complex operators, it's usually best to write simple, single-purpose operators then chain them together when necessary. The pipefunction takes functions as arguments, invokes each function with the value, then passes the returned r…