How to make observable wait for the previous observable to complete

Question

I have a list of observables that needs to invoke APIs synchronously. The APIs fails for asynchronous operation. Hence an observable needs to wait for the previous observable to complete before executing, I have written a recursive solution as shown below, is there a better way to do it.

 private myMethod(params) { let paramsCopy = params.slice(); let param = paramsCopy.shift(); if (param) { let resource: ResourceModel= param.resource; return resource.doPost(JSON.stringify(param.data)) .pipe(mergeMap(res => {return myMethod(paramsCopy)}) ,catchError((err) => handleError())); } else { return //completed actions; } }

Use concatMap - waits for the previous Observable to complete before creating the next one — Vikas
– Vikas, Commented Jun 24, 2019 at 12:48

Vinodini S · Accepted Answer · 2019-06-24 12:44:22Z

You can use concat(observables: ...*): Observable. With this, the observable will wait for the other to complete. Please refer the link - https://www.learnrxjs.io/operators/combination/concat.html

user4676340 · Accepted Answer · 2019-06-24 12:43:00Z

myService.get1().pipe( switchMap(responseOfGet1 => myService.get2()) ).subscribe(responseOfGet2 => { ... });

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