HTTP服务的响应式缓存 [英] Reactive Caching of HTTP Service

问题描述

我正在使用RsJS 5(5.0.1)在Angular 2中进行缓存.它运行良好.

I am using RsJS 5 (5.0.1) to cache in Angular 2. It works well.

缓存功能的实质是:

const observable = Observable.defer(
    () => actualFn().do(() => this.console.log('CACHE MISS', cacheKey))
  )
  .publishReplay(1, this.RECACHE_INTERVAL)
  .refCount().take(1)
  .do(() => this.console.log('CACHE HIT', cacheKey));

actualFn是this.http.get('/some/resource').

就像我说的那样，这很适合我.在RECACHE_INTERVAL的持续时间内从可观察的对象返回缓存.如果在该间隔之后发出请求，则将调用actualFn().

Like I say, this is working perfectly for me. The cache is returned from the observable for duration of the RECACHE_INTERVAL. If a request is made after that interval, the actualFn() will be called.

我要弄清楚的是RECACHE_INTERVAL到期并且actualFn()被称为—的时间.如何返回最后一个值.在RECACHE_INTERVAL到期和重播actualFn()之间存在时间间隔，即可观察对象不返回值.我想摆脱时间上的空白，并始终返回最后一个值.

What I am trying to figure out is when the RECACHE_INTERVAL expires and the actualFn() is called — how to return the last value. There is a space of time between when the RECACHE_INTERVAL expires and the actualFn() is replayed that the observable doesn't return a value. I would like to get rid of that gap in time and always return the last value.

我可能会产生副作用，并在等待HTTP响应返回时存储最后一个具有价值的调用.next(lastValue)，但这似乎很幼稚.我想使用"RxJS"方式，一种纯函数解决方案—如果可能的话.

I could use a side effect and store the last good value call .next(lastValue) while waiting for the HTTP response to return, but this seems naive. I would like to use a "RxJS" way, a pure function solution — if possible.

推荐答案

如果使用普通的rxjs，几乎所有复杂的逻辑都会很快失去控制.我宁愿从头开始实现自定义cache运算符，您可以使用以下要点作为示例

Almost any complicated logic quickly goes out of control if you use plain rxjs. I would rather implement custom cache operator from scratch, you can use this gist as an example.

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