What is the process for manually triggering an observable error?

Question

What is the process for manually triggering an observable error?

I'm currently developing an Angular application where I am making a REST call using HTTP. Here is the code snippet:

login(email, password) {
    let headers = new Headers();
    headers.append('Content-Type', 'application/x-www-form-urlencoded');
    let options = new RequestOptions({ headers: headers });
    let body = `identity=${email}&password=${password}`;
    return this.http.post(`${this._configService.getBaseUrl()}/login`, body, options)
    .map((res: any) => {
        let response: any = JSON.parse(res._body);
        if (response.success == 0) {
          Observable.throw(response);  
        } else if (response.success == 1) {
          console.log('success');
          localStorage.setItem('auth_token', 'authenticated');
          this.loggedIn = true;
          return response;
        }
    });
}

The goal is for my component to receive both successful responses and errors in the subscribe method:

this._authenticateService.login(this.loginObj['identity'],this.loginObj['password']).subscribe(
  (success)=>{      
    this.credentialsError=null;  
    this.loginObj={};  
    this._router.navigate(['dashboard']);    
  },
  (error)=>{
    console.log(error);        
    this.credentialsError=error;     
  }
);

Unfortunately, the API always returns success regardless of the conditions set. How can I properly handle error messages when response.success == 0, so that they are accessible within the error argument of my subscribe callback?

javascript angular typescript rxjs

Answer 1

Answer №1

if (result.status == 0) {
   trigger Observable.throw(result);  
 }

Update for rxjs 6:

if (result.status == 0) {
   throw throwError(result);  
 }

Answer 2

if (result.status == 0) {
   trigger Observable.throw(result);  
 }

Update for rxjs 6:

if (result.status == 0) {
   throw throwError(result);  
 }

Answer 3

Answer №2

Upgrade to rxjs 6

import { throwError } from 'rxjs';

if (response.success == 0) {
  return throwError(response);  
}

Stick with rxjs 5 for now

import { ErrorObservable } from 'rxjs/observable/ErrorObservable';

if (response.success == 0) {
  return new ErrorObservable(response);  
}

The choice of what you return with ErrorObservable is completely up to you

Answer 4

Upgrade to rxjs 6

import { throwError } from 'rxjs';

if (response.success == 0) {
  return throwError(response);  
}

Stick with rxjs 5 for now

import { ErrorObservable } from 'rxjs/observable/ErrorObservable';

if (response.success == 0) {
  return new ErrorObservable(response);  
}

The choice of what you return with ErrorObservable is completely up to you

Answer 5

Answer №3

rxjs version 7

throwError(() => new Error(response))

For further details, visit https://rxjs.dev/deprecations/breaking-changes#throwerror

Answer 6

rxjs version 7

throwError(() => new Error(response))

For further details, visit https://rxjs.dev/deprecations/breaking-changes#throwerror

Answer 7

Answer №4

using rxjs version 6

import { throwError } from 'rxjs';
throwError('hi there');

Answer 8

using rxjs version 6

import { throwError } from 'rxjs';
throwError('hi there');

Answer 9

Answer №5

Using rxjs 5 for error handling:

You can handle errors in the following two ways:

throw response;

or

throw Observable.throw(response);

Answer 10

Using rxjs 5 for error handling:

You can handle errors in the following two ways:

throw response;

or

throw Observable.throw(response);

Answer 11

Answer №6

Below is an example showcasing the official demonstration (which outputs number 7 followed by an error 'oops!'):

import { throwError, concat, of } from 'rxjs';

const sequence = concat(of(7), throwError(new Error('oops!')));
sequence.subscribe(value => console.log(value), error => console.error(error));

Source: https://rxjs-dev.firebaseapp.com/api/index/function/throwError

Answer 12

Below is an example showcasing the official demonstration (which outputs number 7 followed by an error 'oops!'):

import { throwError, concat, of } from 'rxjs';

const sequence = concat(of(7), throwError(new Error('oops!')));
sequence.subscribe(value => console.log(value), error => console.error(error));

Source: https://rxjs-dev.firebaseapp.com/api/index/function/throwError

Answer 13

Answer №7

To manage errors efficiently, make use of the catch operator:

this.calcSub = this.http.post(this.constants.userUrl + "UpdateCalculation", body, { headers: headers })
   .map((response: Response) => {
      var result = <DataResponseObject>response.json();
         return result;
   })
   .catch(this.handleError)
   .subscribe(
      dro => this.dro = dro,
      () => this.completeAddCalculation()
   );

Remember to implement error handling like this:

private handleError(error: Response) {
    console.error(error); // log to console instead
    return Observable.throw(error.json().error || 'Server Error');
}

Answer 14

To manage errors efficiently, make use of the catch operator:

this.calcSub = this.http.post(this.constants.userUrl + "UpdateCalculation", body, { headers: headers })
   .map((response: Response) => {
      var result = <DataResponseObject>response.json();
         return result;
   })
   .catch(this.handleError)
   .subscribe(
      dro => this.dro = dro,
      () => this.completeAddCalculation()
   );

Remember to implement error handling like this:

private handleError(error: Response) {
    console.error(error); // log to console instead
    return Observable.throw(error.json().error || 'Server Error');
}

Answer 15

Answer №8

My troubleshooting efforts mainly pinpointed problems with the imports, leading me to discover a code snippet that finally resolved the issues...

import {_throw} from 'rxjs/observable/throw';
login(email, password) {
...
    return this.http.post(`${this._configService.getBaseUrl()}/login`, body, options)
    .map((res: any) => {
...
        if (response.success == 0) {
           _throw(response);  
        } else if (response.success == 1) {
...
        }
    });
}

If you're grappling with errors such as the following, implementing the above mentioned solution may be your key to success...

ERROR TypeError: WEBPACK_IMPORTED_MODULE_2_rxjs_Observable.Observable.throw is not a function

Answer 16

My troubleshooting efforts mainly pinpointed problems with the imports, leading me to discover a code snippet that finally resolved the issues...

import {_throw} from 'rxjs/observable/throw';
login(email, password) {
...
    return this.http.post(`${this._configService.getBaseUrl()}/login`, body, options)
    .map((res: any) => {
...
        if (response.success == 0) {
           _throw(response);  
        } else if (response.success == 1) {
...
        }
    });
}

If you're grappling with errors such as the following, implementing the above mentioned solution may be your key to success...

ERROR TypeError: WEBPACK_IMPORTED_MODULE_2_rxjs_Observable.Observable.throw is not a function

Answer 17

Answer №9

When encountering an error, it is common to handle it right at the moment it occurs. However, there are situations where this may not be the best approach.

One such example is the timeoutWith() operator, which often requires handling errors in a different manner.

results$ = server.getResults().pipe(timeoutWith(10000, ....) )

This operator accepts an 'error factory', which is essentially a function.

 errorFactory = () => 'Your error occurred at exactly ' + new Date()

For instance:

results$ = server.searchCustomers(searchCriteria).pipe(timeoutWith(10000, 
              () => 'Sorry took too long for search ' + JSON.stringify(searchCriteria)) )

It's important to note that when using timeoutWith, the original server response will not be returned. Therefore, specific server errors might go unnoticed. While this method can aid in debugging, caution must be taken not to expose these errors to end users.

An error factory proves beneficial as it delays code evaluation until an actual error arises. This allows for including 'expensive' or debugging operations within the factory, ensuring they only execute when necessary.

If you require a 'factory' for generating errors outside of a timeout scenario, you can utilize the following approach:

 EMPTY.pipe(throwIfEmpty(errorFactory))

Answer 18

When encountering an error, it is common to handle it right at the moment it occurs. However, there are situations where this may not be the best approach.

One such example is the timeoutWith() operator, which often requires handling errors in a different manner.

results$ = server.getResults().pipe(timeoutWith(10000, ....) )

This operator accepts an 'error factory', which is essentially a function.

 errorFactory = () => 'Your error occurred at exactly ' + new Date()

For instance:

results$ = server.searchCustomers(searchCriteria).pipe(timeoutWith(10000, 
              () => 'Sorry took too long for search ' + JSON.stringify(searchCriteria)) )

It's important to note that when using timeoutWith, the original server response will not be returned. Therefore, specific server errors might go unnoticed. While this method can aid in debugging, caution must be taken not to expose these errors to end users.

An error factory proves beneficial as it delays code evaluation until an actual error arises. This allows for including 'expensive' or debugging operations within the factory, ensuring they only execute when necessary.

If you require a 'factory' for generating errors outside of a timeout scenario, you can utilize the following approach:

 EMPTY.pipe(throwIfEmpty(errorFactory))

Answer 19

Answer №10

Within a pipe, leverage catchError(error) => console.log(error) to handle errors

Answer 20

Within a pipe, leverage catchError(error) => console.log(error) to handle errors

Answer 21

Answer №11

When working with rxjs 8, my approach had to change:

.pipe(
  map(response => {
    if (!response.success) throw throwError(() => response);
    return response;
  }
)

It seems that the main difference is that now, in rxjs 8, the throwError function needs a callback instead of an object

Answer 22

When working with rxjs 8, my approach had to change:

.pipe(
  map(response => {
    if (!response.success) throw throwError(() => response);
    return response;
  }
)

It seems that the main difference is that now, in rxjs 8, the throwError function needs a callback instead of an object

What is the process for manually triggering an observable error?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

Answer №9

Answer №10

Answer №11

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