如何在 RxJS 中实现时间到期热可观察（或在响应式扩展中通用）

我想用 RxJs 实现时间过期缓存。这是“正常”缓存的示例：

//let this represents "heavy duty job"
var data = Rx.Observable.return(Math.random() * 1000).delay(2000);

//and we want to cache result
var cachedData = new Rx.AsyncSubject();
data.subscribe(cachedData);

cachedData.subscribe(function(data){
    //after 2 seconds, result is here and data is cached
    //next subscribe returns immediately data
    cachedData.subscribe(function(data2){ /*this is "instant"*/ });
});

When subscribe on cachedData第一次调用，调用“重载作业”，2秒后结果保存在cachedData (AsyncSubject）。任何其他后续subscribe on cachedData立即返回保存的结果（因此缓存实现）。

我想要实现的是在一段时间内“调味”cachedData是有效的，当时间过去后，我想重新运行新数据的“重型作业”，并在新的时间段再次缓存它，等等......

期望的行为：

//pseudo code
cachedData.youShouldExpireInXSeconds(10);


//let's assume that all code is sequential from here

//this is 1.st run
cachedData.subscribe(function (data) {
    //this first subscription actually runs "heavy duty job", and
    //after 2 seconds first result data is here
});

//this is 2.nd run, just after 1.st run finished
cachedData.subscribe(function (data) {
    //this result is cached
});

//15 seconds later
// cacheData should expired
cachedData.subscribe(function (data) {
    //i'm expecting same behaviour as it was 1.st run:
    // - this runs new "heavy duty job"
    // - and after 2 seconds we got new data result
});


//....
//etc

我是 Rx(Js) 的新手，无法弄清楚如何通过冷却来实现这个热可观察值。

您所缺少的只是安排一个任务来取代您的cachedData与一个新的AsyncSubject一段时间后。以下是如何作为新人进行操作Rx.Observable method:

Rx.Observable.prototype.cacheWithExpiration = function(expirationMs, scheduler) {
    var source = this,
        cachedData = undefined;

    // Use timeout scheduler if scheduler not supplied
    scheduler = scheduler || Rx.Scheduler.timeout;

    return Rx.Observable.create(function (observer) {

        if (!cachedData) {
            // The data is not cached.
            // create a subject to hold the result
            cachedData = new Rx.AsyncSubject();

            // subscribe to the query
            source.subscribe(cachedData);

            // when the query completes, start a timer which will expire the cache
            cachedData.subscribe(function () {
                scheduler.scheduleWithRelative(expirationMs, function () {
                    // clear the cache
                    cachedData = undefined;
                });
            });
        }

        // subscribe the observer to the cached data
        return cachedData.subscribe(observer);
    });
};

Usage:

// a *cold* observable the issues a slow query each time it is subscribed
var data = Rx.Observable.return(42).delay(5000);

// the cached query
var cachedData = data.cacheWithExpiration(15000);

// first observer must wait
cachedData.subscribe();

// wait 3 seconds

// second observer gets result instantly
cachedData.subscribe();

// wait 15 seconds

// observer must wait again
cachedData.subscribe();