一些使用案例
- 轻易实现让服务器retry客户端发起的HTTP调用：
return this.http.get('/api/v1/tasks.json')
.retry(5)
.map( res => res.json());
...
- 每隔10秒钟，轮询一次
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 time
tasksSubscription.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方法返回一个Observable对象，封装了一个10秒间隔的周期性调用，调用内部会执行http操作读取tasks.json文件，将结果以json格式返回。
The caller of our pollTasks() method just gets an observable, which is emitting content every 10 seconds.
调用pollTasks方法，只会返回一个Observable对象，这个Observable对象subscribe之后，会每隔10秒产生内容。调用unsubscribe关闭。
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是一个强力方法，这里将其当作一种engine使用：所有基于之前发生的事件触发的调用都会自动被cancel，包括正在进行中的in-flight HTTP调用。很难想象使用promise实现类似的方法，会花费多大的工作量。