Angular 7 sequntially subscribing

问题

I am subscribing two methods on ngonit but the result of the other method getTest() is coming very late. I am also subscribing other methods and the result of those methods are displaying in between the two methods which I had shared below. Can you please help me how to get the result of the two methods sequentially not with any delay.

export class SomeComponent implements OnInit {
    constructor(public _auth: SomeService, private _route: ActivatedRoute, private) {
        ngOnInit() {
            this._route.queryParams.subscribe(queryParam => {
                    console.log("Test,queryParam);
                    }); this.getTest();

            }

            getTest() {

                return this.http.post("https://someexample.com", {}, {
                    params: parm
                }).subscribe(data => {
                    console.log("Data", data.text());

                });
            }
    }

回答1:

use rxjs switchMap for chaining multiple subscriptions

import { HttpClient} from '@angular/common/http';

export class SomeComponent implements OnInit {
 constructor(public _auth: SomeService, private http: HttpClient,
  private _route: ActivatedRoute, private) {}


 ngOnInit() {
  this._route.queryParams.pipe(
   switchMap((queryParam) => {
    return this.getTest();
   })
  ).subscribe( data => console.log("Data", data.text()));
 }

 getTest() {
    return this.http.post("https://someexample.com", {}, { params: parm});
 }
}

回答2:

You may try this way:

export class SomeComponent implements OnInit {
  constructor(public _auth: SomeService, private _route: ActivatedRoute, private) {
      ngOnInit() {
        this._route.queryParams.subscribe(queryParam => {
            console.log("Test,queryParam);
              this.getTest();
            });

        }

        getTest() {

          return this.http.post("https://someexample.com", {}, {
            params: parm
          }).subscribe(data => {
            console.log("Data", data.text());

          });
        }
      }

来源：https://stackoverflow.com/questions/56790962/angular-7-sequntially-subscribing