Error guards ​

Farfetched uses its own object to represent errors for different reasons. To distinguish between these errors, Farfetched provides a set of error guards.

All error guards are functions that take an object with a error field as an argument and return a boolean value.

isInvalidDataError ​

InvalidDataError is thrown when the response data is invalid against the given Contract or Validator.

import { isInvalidDataError } from '@farfetched/core';

const invalidDataInQuery = sample({
  clock: query.finished.failure,
  filter: isInvalidDataError,
});

isTimeoutError ​

TimeoutError is thrown when the query takes too long to complete.

import { isTimeoutError } from '@farfetched/core';

const timedOut = sample({
  clock: query.finished.failure,
  filter: isTimeoutError,
});

isPreparationError ​

Preparation error is thrown when the response cannot be prepared for some reason. For example, when the response is not a JSON string, but supposed to be.

import { isPreparationError } from '@farfetched/core';

const preparationFailed = sample({
  clock: query.finished.failure,
  filter: isPreparationError,
});

isHttpError ​

HttpError is thrown when the response status code is not 2xx.

import { isHttpError } from '@farfetched/core';

const httpError = sample({
  clock: query.finished.failure,
  filter: isHttpError,
});

isHttpErrorCode ​

This function is a more specific version of isHttpError.

isHttpErrorCode(statusCode: number) ​

It takes a number as an argument and returns a function that checks if the error is a HttpError with the given status code.

import { isHttpErrorCode } from '@farfetched/core';

const notFound = sample({
  clock: query.finished.failure,
  filter: isHttpErrorCode(404),
});

isHttpErrorCode(statusCodes: number[]) since v0.9 ​

It takes an array of numbers as an argument and returns a function that checks if the error is a HttpError with one of the given status codes.

import { isHttpErrorCode } from '@farfetched/core';

const notFoundOrForbidden = sample({
  clock: query.finished.failure,
  filter: isHttpErrorCode([404, 403]),
});

isNetworkError ​

NetworkError is thrown when the query fails because of network problems.

import { isNetworkError } from '@farfetched/core';

const networkProblems = sample({
  clock: query.finished.failure,
  filter: isNetworkError,
});

inConfigurationError since v0.11 ​

ConfigurationError is thrown when the query is misconfigured. E.g., when the URL is not URL.

import { inConfigurationError } from '@farfetched/core';

const configurationProblems = sample({
  clock: query.finished.failure,
  filter: inConfigurationError,
});