一些使用案例

輕易實現讓服務器retry客戶端發起的HTTP調用：

return this.http.get('/api/v1/tasks.json').retry(5).map( res => res.json());...

每隔10秒鐘，輪詢一次

pollTasks() {return Observable.interval(10000).flatMapLatest(() => http.get('/api/v1/tasks.json')).map(res => res.json())}// caller can do subscription and store it as a handle:let tasksSubscription =pollTasks().subscribe( data => this.payload = data);// turn it off at a later timetasksSubscription.unsubscribe();

the pollTasks() method emits a call every 10 seconds, which triggers the call inside of flatMapLatest – we’re basically ignoring the result of that event, and using it to trigger the http.get method to fetch our data. We’ll map it into JSON each time.

pollTasks方法返回一個Observable對象，封裝了一個10秒間隔的周期性調用，調用內部會執行http操作讀取tasks.json文件，將結果以json格式返回。

The caller of our pollTasks() method just gets an observable, which is emitting content every 10 seconds.

調用pollTasks方法，只會返回一個Observable對象，這個Observable對象subscribe之后，會每隔10秒產生內容。調用unsubscribe關閉。

Also the flatMapLatest call is really interesting – any calls generated by previous events are canceled, including their in-flight HTTP method calls. Try doing that with a promise!

flagMapLatest是一個強力方法，這里將其當作一種engine使用：所有基于之前發生的事件觸發的調用都會自動被cancel，包括正在進行中的in-flight HTTP調用。很難想象使用promise實現類似的方法，會花費多大的工作量。

參考文獻

總結

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