Steps for combining a sequence of subsequent subscriptions in RxJS

In my approach, I followed the code below.

this.service1.info
  .subscribe(a => this.service2.getDetails(a.id)
    .subscribe(b => {
      this.doStuff(b);
    })
  );

Lately, it has come to my attention that we will be adding more steps that gradually provide additional details to the client. This leads me to anticipate the emergence of the following cumbersome pattern.

this.service1.info
  .subscribe(a => this.service2.getDetails(a.id)
    ...
            .subscribe(z => { 
              this.doStuff (z);
            })
  );

Is there an elegant way in RxJS to handle such scenarios? I am looking for a solution where an operation is performed only after all steps in the chain have been completed. I have gone through the documentation but haven't found a suitable answer. I have a feeling that the solution is there, and it's just my lack of understanding that is hindering me from finding it.

Answer №1

Indeed, it is not recommended to chain multiple subscribes within RxJS as it is considered an anti-pattern.

An alternative and more elegant approach to chaining observable calls is to utilize pipeable operators. In this case, the use of the switchMap() operator would be appropriate.

According to the information provided on the documentation, switchMap() serves the purpose of

Mapping to an observable, completing the previous inner observable, and emitting values.

this.service1.info
  .pipe(
    switchMap((a) => this.service2.getDetails(a.id)),
    switchMap((a) => this.service3.getDetails(a.id)),
    // switchMap((a) => this.service4.getDetails(a.id)),
    // additional chained methods can follow here
  ).subscribe(z => {
    // handling further actions when observables are returned
    this.doStuff(z);
  });

In the above pipe statement, you can observe that we only invoke subscribe() once, which then yields the observable values. At this point, the doStuff method is executed.

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