Subscribe inside subscribe and return an observable in Angular

Question

Really need help on this. I have been trying different things but its not working.

function1() {
  return this.apiService.get().pipe(map(data => {
    return this.function2();
  }));
  }

function2() {
   const urls = [];

   for (let i = 1; i <= 5; i++) {
      urls.push(
        this.apiService
          .get('/users/?page=' + i)
          .pipe(map(data => data))
      );
    }

   forkJoin(...urls).subscribe(data => {
     data.forEach(element => {
        results = results.concat(element.results);
      });
     return results;
     })
    }


this.someService.function1().subscribe(data => {
console.log(data);
})

So basically, i want to print out data that i subscribe in function1(). But the results of function1() relying on function2() which another subscribe().

I do know why but just dont know how to solve it.when i run the script i alway get undefined, the reason is because the function1() could not wait the function2() to return the results.

I got stuck here. Thanks,

ANSWER: I figured out that i should not return the results in function2 as an array.

function2() {
   const urls = [];

   for (let i = 1; i <= 5; i++) {
      urls.push(
        this.apiService
          .get('/users/?page=' + i)
          .pipe(map(data => data))
      );
    }

   return forkJoin(urls);

and then based on the output of funtion2, i will do the rest in function1 which is the concat()....

Answer 1

You're going to want switchMap - Documentation

Once you have the result from function1 , you want to "switch" to waiting on function2

function1() {
    return this.apiService.get().pipe(switchMap(function1Data => {
        // Send function2 whatever data it needs
        // Example:
        return this.function2(function1Data.function2Argument).pipe(map(function2Data => {
            // Combine function1Data and function2Data as needed
            // Example:
            const result = {
                function1Property: function1Data.property,
                function2Property: function2Data.property
            };
            return result;
        }));
    });
}