Patience is key as you await the completion of an API call in Angular 14

Question

Patience is key as you await the completion of an API call in Angular 14

Within my Angular 14 application, I am faced with a scenario where I need to make two API calls and then combine the results using "combineLatest" from rxjs. The combined data is then assigned to a variable that I must use in a separate function. How can I ensure that this second function is only called once the data has been obtained?

I understand that an immediate solution would be to place the call to the second function inside the "combineLatest" block, but unfortunately, this approach is not feasible for me. Is there a method available to guarantee that the second function is triggered only when the necessary data is present?

Presented below is an excerpt of my code:

this.dataSubscription = combineLatest([aaaSubscription, bbbObservable]).subscribe(result => {
  this.someVariable = result[0];
} 

separateFunction() {
  if(this.someVariable) {
    console.log("Do this")
  }

angular typescript rxjs

Answer 1

Answer №1

To handle the completion of an API call, consider creating an observable such as a Subject. After the API call finishes, you can send a flag or data through the subject and then subscribe to it to execute your desired logic. Here's an example implementation: Code Example

Answer 2

To handle the completion of an API call, consider creating an observable such as a Subject. After the API call finishes, you can send a flag or data through the subject and then subscribe to it to execute your desired logic. Here's an example implementation: Code Example

Answer 3

Answer №2

Utilize map, flatMap, and switchMap for this scenario

this.dataSubscription = combineLatest([aaaSubscription, bbbObservable]).switchMap((result) => {
    this.someVariable = result[0];
    this.customFunction();
    return of(result);
     }).subscribe(result => {
    // Perform desired actions
} 

customFunction() {
  if(this.someVariable) {
    console.log("Perform this action")
  }

Answer 4

Utilize map, flatMap, and switchMap for this scenario

this.dataSubscription = combineLatest([aaaSubscription, bbbObservable]).switchMap((result) => {
    this.someVariable = result[0];
    this.customFunction();
    return of(result);
     }).subscribe(result => {
    // Perform desired actions
} 

customFunction() {
  if(this.someVariable) {
    console.log("Perform this action")
  }

Answer 5

Answer №3

Perhaps the next step is to make a decision?

this.subscription = 
  merge([subscriptionA,observableB])
    .pipe(
      tap(result => this.variable = result[0])
    )
    .subscribe(result => {
      this.executeFunction();
    }); 

executeFunction() {
  if(this.variable) {
    console.log("Perform this action")
  }

Answer 6

Perhaps the next step is to make a decision?

this.subscription = 
  merge([subscriptionA,observableB])
    .pipe(
      tap(result => this.variable = result[0])
    )
    .subscribe(result => {
      this.executeFunction();
    }); 

executeFunction() {
  if(this.variable) {
    console.log("Perform this action")
  }

Answer 7

Answer №4

When working with RxJs and Angular, it's important to leverage the abundance of operators provided by RxJs and the AsyncPipe in Angular to handle reactive data without mixing it with stateful data management. By embracing a declarative approach, you can streamline your code and ensure efficiency. Any side effects like logging or setting state variables should be handled within a tap operator rather than cluttering the subscribe body.

someVariable$ = combineLatest([aaaSubscription, bbbObservable])
  .pipe(
    map(result => result[0]),
    tap(data => { if(data) console.log("Do this") })
  );

To bind someVariable in your template, use

[bindingAttribute]="someVariable$ | async"

. Alternatively, subscribe to it in either OnInit or AfterViewInit, making sure to include a call to takeUntil with an observable that completes in OnDestroy:

stop$ = new Subject<any>();

ngOnInit() {
  this.someVariable$
    .pipe(
      takeUntil(this.stop$)
    ).subscribe();
}

ngOnDestroy() {
  this.stop$.next(true);
  this.stop$.complete();
}

Answer 8

When working with RxJs and Angular, it's important to leverage the abundance of operators provided by RxJs and the AsyncPipe in Angular to handle reactive data without mixing it with stateful data management. By embracing a declarative approach, you can streamline your code and ensure efficiency. Any side effects like logging or setting state variables should be handled within a tap operator rather than cluttering the subscribe body.

someVariable$ = combineLatest([aaaSubscription, bbbObservable])
  .pipe(
    map(result => result[0]),
    tap(data => { if(data) console.log("Do this") })
  );

To bind someVariable in your template, use

[bindingAttribute]="someVariable$ | async"

. Alternatively, subscribe to it in either OnInit or AfterViewInit, making sure to include a call to takeUntil with an observable that completes in OnDestroy:

stop$ = new Subject<any>();

ngOnInit() {
  this.someVariable$
    .pipe(
      takeUntil(this.stop$)
    ).subscribe();
}

ngOnDestroy() {
  this.stop$.next(true);
  this.stop$.complete();
}

Patience is key as you await the completion of an API call in Angular 14

Answer №1

Answer №2

Answer №3

Answer №4

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