RxJS error utils
Utils that help work with errors in rxjs observable's.
Classes
-
RxJSFilterError
- custom error used by error operators.
Available operators
-
filterWithException
- works likefilter
from rxjs, but throw an error instead of ignoring the value. -
rethrowException
- will catch any error in the observable, create a newRxJSFilterError
(or any custom) with custom message and log it with a custom logger function that you can optionally pass in. If it catchesRxJSFilterError
(or any custom), it will just rethrow that exception as is.
Usage examples
filterWithException
If the condition does not pass, will throw RxJSFilterError
exception with passed in message.
import { of } from 'rxjs';
import { filterWithException } from '@rnw-community/rxjs-errors';
of('C')
.pipe(
filterWithException(
letter => letter === 'A',
letter => `Wanted A, but got ${letter}`
)
)
.subscribe(value => console.log(value));
Passing custom error class:
import { filterWithException } from '@rnw-community/rxjs-errors';
import { BadRequestException } from '@nestjs/common';
import { of } from 'rxjs';
of('F')
.pipe(
filterWithException(
letter => letter === 'A',
letter => `Wanted A, but got ${letter}`,
BadRequestException
)
)
.subscribe(value => console.log(value));
Passing a type guard:
import { filterWithException } from '@rnw-community/rxjs-errors';
import { of } from 'rxjs';
const value: unknown = '';
const isString = (val: unknown): val is string => typeof val === 'string';
of(value) // `unknown` here
.pipe(filterWithException(isString, value => `Wanted string, but got ${typeof value}`))
.subscribe((value) /* `string` here */ => {
console.log(value);
});
You could also just pass in a message instead of a function:
import { of } from 'rxjs';
import { filterWithException } from '@rnw-community/rxjs-errors';
of('C')
.pipe(filterWithException(letter => letter === 'A', 'Invalid letter recevied'))
.subscribe(value => console.log(value));
rethrowException
In this example if the passed in letter is not A, then the RxJSFilterError
will be thrown with "Invalid character" text.
rethrowException
will log it and throw it again as is.
If the this.repository.doSomething(letter)
call will throw an error (not an instance of RxJSFilterError
) it will log the
thrown error, and then create a new one of type RxJSFilterError
with "Could not check letter" text.
import { filterWithException, rethrowException } from '@rnw-community/rxjs-errors/src';
import { of } from 'rxjs';
class LetterService {
constructor(private readonly repository: ILetterRepository) {}
checkLetter$(letter: string): Observable<string> {
return of(letter).pipe(
filterWithException(letter !== 'A', 'Invalid character'),
concatMap(letter => this.repository.doSomething(letter)),
rethrowException('Could not check letter', console.error)
);
}
}
In this example any error except for LetterError
will be caught, logged and a LetterError
will be thrown with a "Could
not check letter" message.
import { filterWithException, rethrowException } from '@rnw-community/rxjs-errors/src';
import { of } from 'rxjs';
class LetterError extends Error {}
class LetterService {
constructor(private readonly repository: ILetterRepository) {}
checkLetter$(letter: string): Observable<string> {
return of(letter).pipe(
filterWithException(letter !== 'A', 'Invalid character'),
concatMap(letter => this.repository.doSomething(letter)),
rethrowException('Could not check letter', console.error, LetterError)
);
}
}
You could also pass in a function, that will accept the caught error, to create an error message:
import { filterWithException, rethrowException } from '@rnw-community/rxjs-errors';
import { getErrorMessage } from '@rnw-community/shared';
import { of } from 'rxjs';
class LetterService {
constructor(private readonly repository: ILetterRepository) {}
checkLetter$(letter: string): Observable<string> {
return of(letter).pipe(
filterWithException(letter !== 'A', 'Invalid character'),
concatMap(letter => this.repository.doSomething(letter)),
rethrowException((err: unknown) => getErrorMessage(err), console.error)
);
}
}
If you don't want to log anything, you can just not pass in a log function:
import { filterWithException, rethrowException } from '@rnw-community/rxjs-errors';
import { getErrorMessage } from '@rnw-community/shared';
import { of } from 'rxjs';
class LetterService {
constructor(private readonly repository: ILetterRepository) {}
checkLetter$(letter: string): Observable<string> {
return of(letter).pipe(
filterWithException(letter !== 'A', 'Invalid character'),
concatMap(letter => this.repository.doSomething(letter)),
rethrowException('Could not check letter')
);
}
}
License
This library is licensed under The MIT License.