Angular 2 / RXJS - need some help batching requests

问题

I keep reading rxjs documentation but getting lost in all the operators..

this is what i got so far

  let obs = Observable.from([1, 3, 5])

so what i need this to do is take() some set amount from the array. use the results in a post request, when that comes out successful then i need to restart the process. I want to collect all the results, and keep progress as the process is going (for a progress bar)

I don't need the code for all of that. what i really need to know is how to use rxjs to split this array up.. send part of it, and restart the process until theres nothing left to send.

FINAL SOLUTION

  var _this = this

  function productsRequest(arr) {
    return _this.chainableRequest('post', `reports/${clientId}/${retailerId}/`, loadedProductsReport, {
        'identifiers': arr,
        'realTime': true
      })    
  }

  let arrayCount = Math.ceil(identifiers.length/10)
  let obs = Observable.from(identifiers)            
    .bufferCount(10)
    .concatMap(arr => {
      arrayCount--
      return arrayCount > 0 ? productsRequest(arr) : Observable.empty()
    })


  let subscriber = obs.subscribe(
    value => console.log(value)
  )

chainable request method in parent

  chainableRequest(method: string, endpoint: string, action: Function, data = {}, callback?: Function){
let body = (<any>Object).assign({}, {
  headers: this.headers
}, data)


return this._http[method.toLowerCase()](`${this.baseUri}/${endpoint}`, body, body)
          .map((res: Response) => res.json())
  }

回答1:

This largely depends on what you're trying to achieve.

If you want to recursively call an Observable based on some previous Observable and you don't know how many times you're going to call it then use expand() operator.

For example this demo recursively creates 5 requests based on the response from the previous call (count property):

import { Observable } from 'rxjs/Observable';

function mockPostRequest(count) {
    return Observable.of(`{"count":${count},"data":"response"}`)
        .map(val => JSON.parse(val));
}

Observable.of({count: 0})
    .expand(response => {
        console.log('Response:', response.count);
        return response.count < 5 ? mockPostRequest(response.count + 1) : Observable.empty();
    })
    .subscribe(undefined, undefined, val => console.log('Completed'));

Prints to console:

Response: 0
Response: 1
Response: 2
Response: 3
Response: 4
Response: 5
Completed

See live demo: http://plnkr.co/edit/lKNdR8oeOuB2mrnR3ahQ?p=preview

Or if you just want to call a bunch of HTTP request in order one after another (concatMap() operator) or call all of them at once and consume them as they arrive (mergeMap() operator):

Observable.from([
    'https://httpbin.org/get?1',
    'https://httpbin.org/get?2',
    'https://httpbin.org/get?3',
  ])
  .concatMap(url => Observable.of(url))
  .subscribe(response => console.log(response));

Prints to console:

https://httpbin.org/get?1
https://httpbin.org/get?2
https://httpbin.org/get?3

See live demo: http://plnkr.co/edit/JwZ3rtkiSNB1cwX5gCA5?p=preview

来源：https://stackoverflow.com/questions/40295717/angular-2-rxjs-need-some-help-batching-requests

标签

angular

rxjs

observable

rxjs5