React Native Biometric Authentication Change Detector

Common errors

• The package 'react-native-check-biometric-auth-changed' doesn't seem to be linked. Make sure: - You have run 'pod install' - You rebuilt the app after installing the package - You are not using Expo Go

  cause The native module was not correctly linked into your iOS or Android project, or you are running in an unsupported environment like Expo Go.
  fix For iOS, navigate to your `ios/` directory and run `pod install`. Rebuild your entire React Native application after installation (e.g., `npx react-native run-ios` or `npx react-native run-android`). If using Expo, ensure you are in a bare workflow or using a custom development client, not Expo Go.

• TypeError: (0, _reactNativeCheckBiometricAuthChanged.multiply) is not a function

  cause You are attempting to call the boilerplate `multiply` function from the initial `create-react-native-library` template, which is not the actual API exposed by this package.
  fix Replace calls to `multiply` with the correct functions: `checkBiometricAuthChanged()` or `isBiometricAuthAvailable()`. Refer to the package's source code or its intended documentation for accurate API usage.

Warnings

• breaking As this package is in a very early version (0.1.1), breaking changes may occur in minor or even patch releases. Developers should pin exact versions and carefully review release notes before updating.
  Fix: Use exact version pinning (e.g., `"react-native-check-biometric-auth-changed": "0.1.1"`) and manually review updates for breaking changes.
• gotcha The `multiply` function shown in the README is boilerplate and does not represent the package's actual functionality. The true exports are `checkBiometricAuthChanged` and `isBiometricAuthAvailable`.
  Fix: Refer to the source code (e.g., `src/index.ts` in the GitHub repository) or npm package contents to find the correct API exports and their usage.
• gotcha Like many React Native native modules, this package requires proper linking to the native projects (iOS and Android). Failure to do so will result in runtime errors stating the package is not linked.
  Fix: Ensure you have run `pod install` in your `ios/` directory for iOS and rebuilt your Android project after installation. Avoid using Expo Go for development with native modules that aren't part of the Expo SDK.
• gotcha This package is specifically designed to detect *changes* in biometric authentication settings, not to perform authentication prompts itself. You will need another library for the actual biometric authentication UI.
  Fix: Pair this library with a general biometric authentication library (e.g., `react-native-biometrics` or `expo-local-authentication`) if you also need to prompt the user for biometric verification.

Install

• npm install react-native-check-biometric-auth-changed npm
• yarn add react-native-check-biometric-auth-changed yarn
• pnpm add react-native-check-biometric-auth-changed pnpm

Imports

• checkBiometricAuthChanged
  wrong:

  import checkBiometricAuthChanged from 'react-native-check-biometric-auth-changed'; // Not a default export

  correct:

  import { checkBiometricAuthChanged } from 'react-native-check-biometric-auth-changed';

  This is a named export. The README's `multiply` example is boilerplate and not representative of the actual API.
• isBiometricAuthAvailable
  wrong:

  const { isBiometricAuthAvailable } = require('react-native-check-biometric-auth-changed'); // CommonJS is not the primary pattern for modern RN modules.

  correct:

  import { isBiometricAuthAvailable } from 'react-native-check-biometric-auth-changed';

  This named export is used to check if biometric authentication is set up on the device.

Quickstart

This quickstart demonstrates how to check if biometric authentication is available on the device and if the user's biometric settings have changed, alerting the user to re-authenticate if necessary for security reasons.

import { checkBiometricAuthChanged, isBiometricAuthAvailable } from 'react-native-check-biometric-auth-changed';
import { useEffect, useState } from 'react';
import { Alert } from 'react-native';

const BiometricStatusChecker = () => {
  const [biometricsChanged, setBiometricsChanged] = useState(false);
  const [biometricsSupported, setBiometricsSupported] = useState(false);

  useEffect(() => {
    const checkBiometrics = async () => {
      try {
        const available = await isBiometricAuthAvailable();
        setBiometricsSupported(available);
        if (available) {
          const changed = await checkBiometricAuthChanged();
          setBiometricsChanged(changed);
          if (changed) {
            Alert.alert(
              'Security Alert',
              'Your biometric authentication settings have changed. Please re-authenticate or re-enroll for security purposes.'
            );
          } else {
            console.log('Biometric settings are unchanged.');
          }
        } else {
          console.log('Biometric authentication is not available or enrolled.');
        }
      } catch (error) {
        console.error('Failed to check biometric status:', error);
        Alert.alert('Error', 'Could not check biometric status: ' + error.message);
      }
    };
    checkBiometrics();
  }, []);

  return (
    // Your component rendering logic based on biometricsChanged and biometricsSupported
    // For example, display a message or trigger a re-authentication flow
    null
  );
};

export default BiometricStatusChecker;