CODEWITHSUNDEEP
angularrxjsconcatenationsubscription
Lokicor
Lokicor

Reputation: 137

Concat subscriptions in Angular

I need to subscribe to two different things in the ngOnInit of a given component:

  1. To a get request included in an Angular service already created, from which I will fetch a list of items (sourceOptions in the code).
  2. To the route.queryParams of my url, so I can use one of these params to call a function which will also use the list of items fetched in point 1.

The issue here is that I need somehow to concat them in a given order (1. then 2.) because the function called in 2 setSelected(params["sourceTool"] is using the list of items mentioned.

Could it be done with rxjs concat operator? How should it be coded?

Thanks

ngOnInit(): void {

  this.searchApi.getSourceTools()
      .subscribe(response => {
        response.items.forEach((sourceTool: string) => {
          this.sourceOptions.push({
            description: sourceTool,
            selected: false
          })
        })
      })

  this.route.queryParams
    .subscribe(params => {
       this.setSelected(params["sourceTool"])
    })

}

Upvotes: 1

Views: 459

Answers (1)

wojky
wojky

Reputation: 78

  this.searchApi.getSourceTools()
    .pipe(
      tap(response => {
        response.items.forEach((sourceTool: string) => {
          this.sourceOptions.push({
            description: sourceTool,
            selected: false
          })
        })
      }), 
      switchMap(() => this.route.queryParams)
     )
     .subscribe(params => {
       this.setSelected(params["sourceTool"])
    });

If I understand correctly your problem, you can easily use switchMap operator to change the source observable after initial source emit value (with side effects execution)

Upvotes: 1

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