Is it feasible to assign a value to a variable in Angular based on the data returned from a subscription?

Question

Is it feasible to assign a value to a variable in Angular based on the data returned from a subscription?

somefunction(){
    isUserLoggedin(): boolean {
        this.isUserInDB().subscribe((result: any) => {
          if (result.code === 200) {
            return true;
          }
        });
      return false;
  }

isUserInDB(): this API takes a token from localstorage and returns 200 if the user exists in DB or returns 404 if the user does not exist in DB (someone is trying to try his/her own token.)

In this scenario, I always end up receiving false because the first return statement gets executed before the subscribe method. Is there a different approach I should consider, or am I just overcomplicating things?

angular typescript promise rxjs-observables

Answer 1

Answer №1

Set a class property to false initially:

isUserInDatabase = false

Upon component creation, update the property to true if the response is successful:

ngOnInit() {
    this.checkUserInDatabase().subscribe((response: any) => {
        if (response.statusCode === 200) {
            this.isUserInDatabase = true;
        }
    });
}

Answer 2

Set a class property to false initially:

isUserInDatabase = false

Upon component creation, update the property to true if the response is successful:

ngOnInit() {
    this.checkUserInDatabase().subscribe((response: any) => {
        if (response.statusCode === 200) {
            this.isUserInDatabase = true;
        }
    });
}

Answer 3

Answer №2

Due to the asynchronous nature of this.isUserInDB(), the function isUserLoggedin will always return false. One way to handle this is by returning the observable instead of a boolean, and managing it where the function is called:

isUserLoggedin(): Observable<any> { // replace any with your type
    return this.isUserInDB();
}

Whenever you need to execute tasks based on user login status, you can subscribe to this function and carry out your operations:

isUserLoggedIn.subscribe((result: any) => {
          if (result.code === 200) {
             // Your code
          }

It is recommended that in your login process, you store the user's login status in a service and return it accordingly.

Answer 4

Due to the asynchronous nature of this.isUserInDB(), the function isUserLoggedin will always return false. One way to handle this is by returning the observable instead of a boolean, and managing it where the function is called:

isUserLoggedin(): Observable<any> { // replace any with your type
    return this.isUserInDB();
}

Whenever you need to execute tasks based on user login status, you can subscribe to this function and carry out your operations:

isUserLoggedIn.subscribe((result: any) => {
          if (result.code === 200) {
             // Your code
          }

It is recommended that in your login process, you store the user's login status in a service and return it accordingly.

Answer 5

Answer №3

My approach would be to synchronize it using async/await functionality.

async checkIfUserLoggedIn(): Promise<boolean> {
   const result = await this.verifyUserInDatabase().pipe(first()).toPromise();

   if (result.code === 200) {
      return true;
   } else {
      return false;
   }
}

Example of how to use it:

async someFunction(): Promise<void> {
    const isLoggedIn = await this.checkIfUserLoggedIn();
}

Answer 6

My approach would be to synchronize it using async/await functionality.

async checkIfUserLoggedIn(): Promise<boolean> {
   const result = await this.verifyUserInDatabase().pipe(first()).toPromise();

   if (result.code === 200) {
      return true;
   } else {
      return false;
   }
}

Example of how to use it:

async someFunction(): Promise<void> {
    const isLoggedIn = await this.checkIfUserLoggedIn();
}

Is it feasible to assign a value to a variable in Angular based on the data returned from a subscription?

Answer №1

Answer №2

Answer №3

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