poll.md

代码逻辑

const forceCheckInvokerSubject: Subject<any> = new Subject<any>();

public invokePoll() {
    this.forceCheckInvokerSubject.next();
}

private poll() {
    this.pollSubscription = Observable.interval(1000 * 60)
        .merge(forceCheckInvokerSubject)
        .exhaustMap(() => Observable.fromPromise(this.checkState()))
        .subscribe((response) => {
            if (response == null) return;

            // to do something
        });
}


private async checkState(): Promise<any> {

}

代码分析

• 创建定时器Observable.interval(1000 * 60)，每隔一分钟请求一次服务器
• 创建forceCheckInvokerSubject，merge操作符关联定时器，调用this.forceCheckInvokerSubject.next()，触发轮询
• exhaustMap保证checkState()已完成异步请求，否则忽略最新的next

业务场景

• websoket消息推送失败，主动发送cmd触发消息推送
• ...