Local Storage in React Native: AsyncStorage u0026 SQLite Quiz Quiz

Explore your understanding of local storage techniques in React Native with this quiz focused on AsyncStorage and SQLite, including data storage, retrieval, and best practices. Perfect for developers aiming to reinforce their knowledge of offline data handling and persistent storage mechanisms.

1. Identifying Local Storage Solutions

   Which of the following options is considered a local storage solution that allows you to store simple key-value pairs persistently in React Native applications?

   1. Axios
   2. AsyncStorage
   3. WebSocket
   4. Redux

   Explanation: AsyncStorage is designed for persisting simple key-value data locally on a device in React Native. WebSocket is used for real-time communication and does not store data. Redux is a state management tool but does not persist data without extra middleware. Axios is a tool for making HTTP requests, not for local storage.

2. Data Types in AsyncStorage

   When saving and retrieving data using AsyncStorage, which data type must all stored values ultimately be converted to?

   1. Integer
   2. Array
   3. String
   4. Boolean

   Explanation: AsyncStorage only supports storing data as strings, so you must convert objects, arrays, or other types to strings, typically using JSON. Boolean, Array, and Integer types must all be stringified before storing and parsed back when reading them. Attempting to store these directly would lead to errors.

3. SQL Syntax Familiarity

   Which programming language is used for writing queries with SQLite in React Native applications to manage relational data?

   1. HTML
   2. CSS
   3. SQL
   4. YAML

   Explanation: SQLite relies on SQL, the standard language for querying and modifying relational databases. HTML and CSS are used for structuring and styling web pages, not for database interactions. YAML is a markup language for configuration, unrelated to querying databases.

4. Basic AsyncStorage Operations

   If you want to remove a key-value pair from AsyncStorage, which function should you use?

   1. getItem
   2. removeItem
   3. setState
   4. pushItem

   Explanation: The removeItem function is specifically designed to remove a key-value pair from AsyncStorage. getItem retrieves data but doesn't remove it. setState is used for updating component state, not storage. pushItem is not a standard AsyncStorage function and does not exist.

5. Advantages of SQLite

   What is a primary advantage of using SQLite for local storage in a React Native application handling complex structured data?

   1. It can only store key-value pairs.
   2. It supports relational data and complex queries.
   3. It has no storage size limitations.
   4. It automatically synchronizes with a cloud server.

   Explanation: SQLite is a local database engine that allows storing and querying relational data using SQL, making it suitable for complex data structures. Key-value stores do not allow the same level of complexity. SQLite does not automatically sync data with remote servers, and while it is efficient, it still has storage limits based on device resources.

6. AsyncStorage Functionality

   Which scenario best demonstrates when to choose AsyncStorage over SQLite in a React Native project?

   1. When you want to store images directly in the database.
   2. When you require complex joins between multiple tables.
   3. When you need to perform advanced aggregation queries.
   4. When you need to store a user token or small non-relational configuration data.

   Explanation: AsyncStorage is ideal for simple key-value pairs like user tokens and small config settings. SQLite is better for complex queries and relationships. Storing images in AsyncStorage is discouraged due to performance. Advanced aggregation queries require features only available in relational databases like SQLite.

7. Persistence Behavior

   What happens to data stored using AsyncStorage when a user closes and reopens the React Native app?

   1. The data syncs automatically with cloud storage.
   2. The data is erased when the app closes.
   3. The data persists and can be retrieved upon reopening the app.
   4. The data is converted into a database row.

   Explanation: AsyncStorage is meant for persistent storage, so saved data remains available even after app restarts. It does not erase data on closure, nor does it automatically sync with cloud services. AsyncStorage is not a relational database, so data isn't converted into database rows.

8. SQLite Table Creation

   Which SQL statement should you use to create a new table named 'users' in a SQLite database for storing user data in React Native?

   1. FORM TABLE users;
   2. SELECT TABLE users;
   3. CREATE TABLE users (...);
   4. MAKE users TABLE;

   Explanation: The correct SQL syntax for creating a new table is CREATE TABLE, followed by the table name and column definitions in parentheses. SELECT TABLE is not valid for table creation. MAKE and FORM TABLE do not exist in SQL and are incorrect options.

9. AsyncStorage Usage Limitations

   Which is a notable limitation when using AsyncStorage for storing local data in React Native?

   1. It is not suitable for storing large or complex data structures.
   2. It provides advanced search and query capabilities.
   3. It supports real-time updates across multiple devices.
   4. It allows for creating relational data tables.

   Explanation: AsyncStorage is best for small, simple data and is inefficient for large or complex datasets. It does not provide real-time updates across devices or advanced query features, and it cannot create or manage relational data structures like tables.

10. SQLite Data Querying

    Which SQL command would you use to retrieve all data from the 'products' table in a React Native SQLite database?

    1. FETCH EVERY products;
    2. PICK ALL FROM products;
    3. SELECT * FROM products;
    4. GRAB DATA products;

    Explanation: SELECT * FROM products; is the correct SQL syntax to retrieve all records from the 'products' table. The other options do not follow valid SQL syntax and would result in errors when executing queries.