情景:
我正在努力争取没有中间变量的选项。
let filterStream = Rx.Observable
.combineLatest(
filterX,
filterY,
(filterX, filterY) => {
x: filterX,
y: filterY
}
)
.map((filters) => {
limit: 100,
s: filters.x.a,
f: filters.x.b + filters.y.c,
})
.distinctUntilChanged()
let cheapDataStream = filterStream
.flatMapLatest((filterQuery) =>
Rx.Observable.fromPromise(cheapBackendApiCall(filterQuery)))
// render cheap results
cheapDataStream
.map(result => transformForDisplay(result))
.subscribe(result => {
//render
// how do i invoke expensiveApiCall() with `filterQuery` data here?
// with a delay, and only if filterQuery has not changed?
});
答案 0 :(得分:2)
您可以利用隐式转换来避免在任何地方明确使用fromPromise
。然后你可以使用concat立即返回廉价数据,然后是延迟的昂贵+廉价数据。通过将其嵌套在flatMapLatest
中,如果新查询到达,则流也将取消任何待处理的expensiveCalls
。
var filters = Rx.Observable
.combineLatest(
filterX,
filterY,
(filterX, filterY) => {
x: filterX,
y: filterY
}
)
.map((filters) => {
limit: 100,
s: filters.x.a,
f: filters.x.b + filters.y.c,
})
.distinctUntilChanged()
.flatMapLatest(filters => {
//This kicks off immediately
var cheapPromise = cheapBackendApiCall(filters);
//This was added in the latest version 4.1, the function is only called once it is subscribed to,
//if you are using earlier you will need to wrap it in a defer instead.
var expensivePromiseFn = () => expensiveBackendApiCall(filters);
//For join implicitly calls `fromPromise` so you can pass the same
// sort of arguments.
var cheapAndExpensive = Rx.Observable.forkJoin(
cheapPromise,
expensivePromiseFn,
(cheap, expensive) => ({cheap, expensive}));
//First return the cheap, then wait 1500 millis before subscribing
//which will trigger the expensive operation and join it with the result of the cheap one
//The parent `flatMapLatest` guarantees that this cancels if a new event comes in
return Rx.Observable.concat(cheap, cheapAndExpensive.delaySubscription(1500));
})
.subscribe(x => /*Render results*/);
答案 1 :(得分:0)
你在寻找debounce吗? 这个操作符似乎完全按照你的描述进行操作。
答案 2 :(得分:0)
我提出的解决方案,不确定是否()是合适的,并且廉价+昂贵的数据合并看起来不太反应。
Rx.Observable
.combineLatest(
filterX,
filterY,
(filterX, filterY) => {
x: filterX,
y: filterY
}
)
.map((filters) => {
limit: 100,
s: filters.x.a,
f: filters.x.b + filters.y.c,
})
.distinctUntilChanged()
.flatMapLatest((filterQuery) =>
Rx
.Observable
.fromPromise(cheapBackendApiCall(filterQuery))
.map((results) => {
filterQuery: filterQuery,
results: results
})
)
.do((filtersAndResults) => {
// render filtersAndResults.results
})
.debounce(1500)
.flatMapLatest((filtersAndResults) => {
return Rx
.Observable
.fromPromise(expensiveBackendApiCall(filtersAndResults.filterQuery))
.map(results => {
expensiveData: results,
cheapData: filtersAndResults.results
})
})
.subscribe((result)=> {
// combine results.cheapData + results.expensiveData with simple .map and .find
// and render
})