RxJS:如何使用concatMap或switchMap间隔发送http订阅？有什么关系呢？

Question

我尝试遵循这个示例、stackblitz和Observable文档，但似乎对我不起作用。坦率地说，我是RxJS的新手，不知道如何使用http和subscribe。盯着这个问题看了这么久，我的脑子都糊涂了。从本质上讲，我希望subscribe每隔一段时间就检查一次新数据。也许有比rxjs更好的方法？

import { Component, OnDestroy, OnInit } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

import { Weather } from './interface';
import { Observable } from 'rxjs/Observable';

import { interval } from 'rxjs';
import { take } from 'rxjs/operators';
import { Subject } from 'rxjs';

@Component({
  selector: 'app-weather',
  templateUrl: './weather.component.html',
  styleUrls: ['./weather.component.css']
})
export class WeatherComponent implements  OnInit {
  weathers: any;
  response: any;
  // t = Observable.interval(1000).take(5);
  // numbers = interval(1000);
  // takeFourNumbers = interval(50000).pipe(take(2));


  private serviceUrl = 'https://api.weather.gov/gridpoints/OKX/36,38/forecast';
  n = 10000;
  constructor(private http: HttpClient) {}

  ngOnInit() {

      this.response = this.http.get<Weather>(this.serviceUrl );
      this.response.subscribe(
        results => {
          this.weathers = results.properties.periods.slice(0, 2);

          // this.numbers.subscribe(x => console.log('Next: ', x));
        });
    }
}

Answer 1

您可以使用interval每秒发射一次，然后将每个发射转换为一个HTTP请求。

import { interval } from 'rxjs';
import { switchMap } from 'rxjs/operators';

interval(1000).pipe(
  switchMap(() => this.http.get<Weather>(this.serviceUrl)),
).subscribe(result => {
  // ...
});

根据您想要的行为，您可能希望使用concatMap而不是switchMap。