最好的“压平"方式RxJS Observable内部的数组

问题描述

我的后端经常在RxJS 5 Observable (我使用Angular 2)中以数组的形式返回数据.

My backend frequently returns data as an array inside an RxJS 5 Observable (I'm using Angular 2).

我经常发现自己想用RxJS运算符分别处理数组项，而我使用以下代码( JSBin ):

I often find myself wanting to process the array items individually with RxJS operators and I do so with the following code (JSBin):

const dataFromBackend = Rx.Observable.of([
  { name: 'item1', active: true },
  { name: 'item2', active: false },
  { name: 'item3', active: true }
]);

dataFromBackend
  // At this point, the obs emits a SINGLE array of items
  .do(items => console.log(items))
  // I flatten the array so that the obs emits each item INDIVIDUALLY
  .mergeMap(val => val)
  // At this point, the obs emits each item individually
  .do(item => console.log(item))
  // I can keep transforming each item using RxJS operators.
  // Most likely, I will project the item into another obs with mergeMap()
  .map(item => item.name)
  // When I'm done transforming the items, I gather them in a single array again
  .toArray()
  .subscribe();

mergeMap(val => val)行不是很习惯.

是否有更好的方法将转换应用于Observable发出的数组的成员?

Is there a better way to apply transformations to the members of an array that's emitted by an Observable?

NB.我希望RxJS运算符(相对于数组方法)转换我的项目，因为我需要能够将每个项目投影到另一个可观察的项目中.典型的用例:后端返回项ID列表，我需要从后端请求所有这些项.

NB. I want RxJS operators (vs array methods) to transform my items because I need the ability to project each item into a second observable. Typical use case: backend returns of list of item ids and I need to request all of these items from the backend.

推荐答案

您可以不带任何参数使用concatAll()或mergeAll().

You can use concatAll() or mergeAll() without any parameter.

dataFromBackend.pipe(
  tap(items => console.log(items)),
  mergeAll(), // or concatAll()
)

此方法(包括mergeMap)仅在RxJS 5中有效，因为它以相同的方式对待Observable，数组，类似数组的对象，Promises等.

This (including mergeMap) works only in RxJS 5 because it treats Observables, arrays, array-like objects, Promises, etc. the same way.

最终您还可以:

mergeMap(val => from(val).pipe(
  tap(item => console.log(item)),
  map(item => item.name),
)),
toArray(),

2019年1月:已针对RxJS 6更新

Jan 2019: Updated for RxJS 6

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