use RXJS to return results of two observables together

Question

I would like to read parameters from the URL and with that value then call an observable. If a result has been found I'd like to continue with it and call another observable. Ideally both calls are wrapped and I only have to subscribe once and I get both results back together.

This is my implementation so far:

this.route.paramMap.pipe(
  switchMap(params => {
    return forkJoin(
      this.treeService.getTree(params.get('treeName')),
      this.treeService.getTree(params.get('treeName')).pipe(
        mergeMap(tree => this.fruitService.getFruit(tree.id))
      )
    )
  })
).subscribe(res => console.log(res));

this works just fine, but I have to make 2 of the same calls .. how can I improve it so it only does one call to the treeService?

kvetis · Accepted Answer · 2020-03-26 15:35:07Z

3

You can use an inner map like this:

this.route.paramMap.pipe(
  switchMap(params => {
    return this.treeService.getTree(params.get('treeName')).pipe(
      switchMap(tree => this.fruitService.getFruit(tree.id).pipe(
        map(fruit => ([tree, fruit]))
      ))
    )
  })
).subscribe(res => console.log(res));

edited Mar 26, 2020 at 15:35

kvetis

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answered Mar 26, 2020 at 15:31

bryan60

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