Applying Data Filtering and Aggregation in a User Management System

Welcome to today’s lesson on applying data filtering and aggregation in a real-world scenario through a user management system. We’ll start by building a foundational structure that can handle basic user operations, then gradually expand it by introducing more advanced functionalities to allow filtering and aggregating user data.

In our starter task, we’ll implement a class to manage basic operations on a collection of user data, specifically handling the addition of new users, retrieving user profiles, and updating existing user profiles. Here are the methods we’ll begin with:

• add_user(user_id, age, country, subscribed) — Adds a new user with specified attributes. Returns true if the user is added successfully; returns false if a user with the same user_id already exists.
• get_user(user_id) — Retrieves the user’s profile as a hash if the user exists; returns nil if the user does not exist.
• update_user(user_id, age = nil, country = nil, subscribed = nil) — Updates the user’s profile with provided parameters. Returns true if the user exists and was updated, and false otherwise.

Let’s begin by creating a UserManager class that manages user data within a hash structure, @users, where each key is a user_id and each value is a hash representing the user’s profile.

class UserManager
  def initialize
    @users = {}
  end
end

The initialize method sets up an empty hash, @users, which will store all user profiles.

The add_user and get_user methods handle adding new users and retrieving existing user profiles.

def add_user(user_id, age, country, subscribed)
  return false if @users.key?(user_id)

  @users[user_id] = { age: age, country: country, subscribed: subscribed }
  true
end

def get_user(user_id)
  @users[user_id]
end

In add_user, we check if a user with the specified user_id already exists. If not, we create a new entry in @users with the user’s details and return true. If the user already exists, it returns false. The get_user method retrieves a user’s profile from @users, returning the profile if found or nil if the user does not exist.