Implementing Data Persistence

import { AsyncStorage } from 'react-native';

// Save data
await AsyncStorage.setItem('userToken', 'abc123');

// Retrieve data
const token = await AsyncStorage.getItem('userToken');
console.log(token); // "abc123"

import AsyncStorage from '@react-native-async-storage/async-storage';

const saveUserProfile = async (userProfile) => {
  try {
    const jsonValue = JSON.stringify(userProfile);
    await AsyncStorage.setItem('userProfile', jsonValue);
  } catch (e) {
    console.error('Failed to save user profile', e);
  }
};

// Usage
const userProfile = {
  id: '12345',
  name: 'John Doe',
  preferences: {
    theme: 'dark',
    notifications: true
  }
};

saveUserProfile(userProfile);

import AsyncStorage from '@react-native-async-storage/async-storage';

const loadUserPreferences = async () => {
  try {
    const jsonValue = await AsyncStorage.getItem('userPreferences');
    if (jsonValue != null) {
      const preferences = JSON.parse(jsonValue);
      return preferences;
    }
  } catch (e) {
    console.error('Failed to load user preferences', e);
  }
  return null;
};

// Usage
const prefs = await loadUserPreferences();
console.log(prefs?.theme); // "dark"

import { encrypt, decrypt } from 'react-native-crypto'; // hypothetical library

const secretKey = 'your-256-bit-secret-key-here';
const dataToEncrypt = JSON.stringify({ userId: '123', token: 'abc123' });

const encrypted = encrypt(secretKey, dataToEncrypt);
console.log(encrypted); // { iv: '...', data: '...' }

const decrypted = decrypt(secretKey, encrypted.iv, encrypted.data);
console.log(JSON.parse(decrypted)); // { userId: '123', token: 'abc123' }

import MMKV from 'react-native-mmkv';

const storage = new MMKV();

// Set a value
storage.set('user.name', 'John Doe');

// Get a value
const name = storage.getString('user.name');
console.log(name); // John Doe

// Remove a value
storage.delete('user.name');

import { AsyncStorage } from 'react-native';\n\nconst checkStorageUsage = async () => {\n  try {\n    const keys = await AsyncStorage.getAllKeys();\n    let totalSize = 0;\n    for (const key of keys) {\n      const value = await AsyncStorage.getItem(key);\n      totalSize += new Blob([value]).size;\n    }\n    console.log(`Total storage used: ${totalSize} bytes`);\n  } catch (error) {\n    console.error('Error checking storage:', error);\n  }\n};

import AsyncStorage from '@react-native-async-storage/async-storage';

const cacheKey = 'userProfile';
const userData = {
  id: 123,
  name: 'John Doe',
  email: 'john@example.com'
};

// Save to cache
const saveToCache = async () => {
  try {
    await AsyncStorage.setItem(cacheKey, JSON.stringify(userData));
    console.log('Data cached successfully');
  } catch (error) {
    console.error('Failed to cache data:', error);
  }
};

// Retrieve from cache
const getFromCache = async () => {
  try {
    const cachedData = await AsyncStorage.getItem(cacheKey);
    if (cachedData) {
      return JSON.parse(cachedData);
    }
    return null;
  } catch (error) {
    console.error('Failed to retrieve from cache:', error);
    return null;
  }
};

const CACHE_TIMEOUT = 5 * 60 * 1000; // 5 minutes

const setCachedWithExpiry = async (key, value) => {
  const item = {
    value: JSON.stringify(value),
    timestamp: Date.now()
  };
  await AsyncStorage.setItem(key, JSON.stringify(item));
};

const getCachedWithExpiry = async (key) => {
  const cachedItem = await AsyncStorage.getItem(key);
  if (!cachedItem) return null;

  const { value, timestamp } = JSON.parse(cachedItem);
  if (Date.now() - timestamp > CACHE_TIMEOUT) {
    await AsyncStorage.removeItem(key);
    return null;
  }

  return JSON.parse(value);
};

import * as SecureStore from 'expo-secure-store';

// Store a value
await SecureStore.setItemAsync('authToken', 'abc123xyz');

// Retrieve a value
const token = await SecureStore.getItemAsync('authToken');
console.log(token); // "abc123xyz"

import AsyncStorage from '@react-native-async-storage/async-storage';
import SQLite from 'react-native-sqlite-storage';

// Old: AsyncStorage
const oldData = await AsyncStorage.getItem('userPreferences');

// New: SQLite migration
const newData = await new Promise((resolve, reject) => {
  SQLite.openDatabase({name: 'app.db'}).transaction(tx => {
    tx.executeSql(
      'SELECT * FROM userPreferences',
      [],
      (_, results) => resolve(results.rows),
      (_, error) => reject(error)
    );
  });
});

import AsyncStorage from '@react-native-async-storage/async-storage';

// Clear all storage
await AsyncStorage.clear();

// Clear specific key
await AsyncStorage.removeItem('userToken');

import { database } from './firebaseConfig';

const ref = database.ref('users');
ref.on('value', (snapshot) => {
  const data = snapshot.val();
  console.log('User data updated:', data);
});

// To remove the listener later
ref.off('value');