rxjs expand operator with switchMap - axios

Question

I have a list of students, for each student, I have to access the address. I will get the student list in pagination. so I used the 'expand' operator to get all students. but I am not able to get the address for each student.
Student List
{
students: [
{
id: 1,
name: 'ABC'
},
{
id: 2,
name: 'XYZ'
}
],
nextPageToken: 'Aqw12'
}
Now using the student's id I have to fetch the address.
Here is my sample code to get the student's list with the rxjs expand operator.
const connection = this.searchStudent(nextPageToken).pipe(
expand((students: StudentsDto) => {
if (students.nextPageToken){
nextPageToken = students.nextPageToken;
return this.searchStudent(nextPageToken);
}else{
return new Observable as Observable<StudentsDto>;
}
})
);
const subscription = connection.subscribe({
next(response: StudentsDto) {
response.students.forEach(async (student: StudentDto) => {
console.log(student);
});
},
error(e) {
console.log(e)
},
complete() {
subscription.unsubscribe();
},
});
Now I am not able to get, what operator should I apply to get the address.
for address, I have implemented API in this.getAddress(studentId) function which return Observables.
Please help,
Thanks.

Answer 1

const connection = this.searchStudent(nextPageToken).pipe(
expand((response: StudentsDto) => {
if (response.nextPageToken){
nextPageToken = response.nextPageToken;
return this.searchStudent(nextPageToken);
}else{
return new Observable as Observable<StudentsDto>;
}
}),
mergeMap((response: StudentsDto) => {
return response.students.map(student => this.getAddress(student.id))
}),
mergeAll(),
);
const subscription = connection.subscribe({
next(response: AddressDto) {
// Perform/save operation on Address object
},
error(e) {
console.log(e)
},
complete() {
subscription.unsubscribe();
},
});