javascript - RxJS5: .combineLatest() 有投影功能？

Question

我需要一种方法将值从一个 observable 传递给两个函数，每个函数都接受一个值，每个函数依次返回一个 observable(只发出一个值，然后完成)。我希望 .combineLatest() 允许我传递一个投影函数，但它没有。

示例代码(不工作):

const ac = [1, 2, 3]; // only as example, I have complex types in my array not numbers

Observable.from(ac)
    .combineLatest(
        // processFn should get a number as argument and return Observable<number>
        // does not work because .combineLatest does not accept two functions as arguments :(
        n => processFn1(n),
        n => processFn2(n)
    )
    .map(([result1, result2] => {
        // result1, result2 should be flat numbers here, not Observables
    })
);

知道怎么做吗？

Answer 1

您使用 combineLatest 运算符的想法是正确的，但它在错误的地方。如果你需要扁平化 observables，你应该使用 mergeMap。这是一个符合您预期的 JSBIN:http://jsbin.com/rutovot/4/edit?html,js,console

代码如下所示:

const ac = [1, 2, 3];

Rx.Observable.from(ac)
  // use mergeMap, it takes a function that accepts a value and
  // returns an observable. MergeMap will listen to this observable
  // under the hood and next the result of this observable down the
  // the chain
  .mergeMap(val => {
    // Here we return an observable that combines the result of the
    // call to both the functions
    return Rx.Observable.combineLatest(fake(val), fake2(val));
  })
  .subscribe(val => console.log(val));