Live Coding: Simple User Management System

live_coding_user_management_system.md

Live coding: Simple User Management System

Suggested level: Middle

Task Overview: Building a Simple User Management System

The challenge is divided into three steps, each increasing in complexity. The goal is to evaluate problem-solving skills, OOP understanding, and ability to refactor code.

Step 1

Basic Functionality (Easy)

Task: Write a PHP function that stores user data in an array and retrieves user information by ID.

Requirements:

• A function addUser(string $name, int $age): int that adds a user and returns a unique ID.
• A function getUser(int $id): ?array that retrieves user details.
• Data should be stored in-memory (simple array).

Example usage:

$id = addUser('Alice', 30);
$user = getUser($id);
// Output: ['id' => 1, 'name' => 'Alice', 'age' => 30]

Expected skills and knowledge:

• Basic PHP skills
• Understanding of arrays and functions
• Handling of IDs and null values

Step 2

Introduce OOP (Intermediate)

Task: Refactor the code into a UserManager class that follows OOP principles.

Requirements:

• Create a UserManager class.
• Use private properties for user storage.
• Implement the methods as class methods.

Example usage:

$manager = new UserManager();
$id = $manager->addUser('Bob', 25);
$user = $manager->getUser($id);

Expected skills and knowledge:

• Object-oriented programming (OOP)
• Encapsulation & class structure
• Proper method design

Step 3

Advanced - Implement Dependency Injection & Refactoring (Complex)

Task:

Refactor the UserManager class to:

1. Use Dependency Injection for user storage (e.g., database or file-based storage).
2. Introduce an interface for different storage implementations.
3. Implement at least one concrete storage class (e.g., ArrayStorage).

Requirements:

• Define a UserStorageInterface with addUser() and getUser().
• Implement ArrayStorage as an example.
• Modify UserManager to use the storage via Dependency Injection.

Example usage:

$storage = new ArrayStorage();
$manager = new UserManager($storage);

$id = $manager->addUser('Charlie', 40);
$user = $manager->getUser($id);

Expected skills and knowledge:

• Understanding of Dependency Injection
• Use of Interfaces & SOLID principles
• Ability to refactor and write maintainable code

Bonus

Bonus Challenge (if time allows)

• Add a FileStorage class that persists user data to a JSON file.
• Implement error handling for missing users.