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Design an object-oriented social network (Facebook-like) that supports user profiles with privacy settings, mutual friendships with request lifecycle, posts (text/image/video/link) with likes and nested comments, groups with role-based access, 1:1 direct messaging, a personalised news feed, and a notification system.
The friend graph is bidirectional (mutual). Posts respect privacy levels (Public, Friends-only, Private). The news feed aggregates posts from friends and joined groups with privacy filtering. Notifications cover friend requests, likes, comments, tags, and messages.
User registration & profile
Sign up, set bio, profile picture, and privacy settings
Friend management
Send/accept/reject friend requests, unfriend, and block users
Create posts
Create text, image, video, or link posts with privacy controls
Like & comment
Like posts/comments, add comments with nested replies
News feed
Personalised feed aggregating posts from friends and groups, sorted by recency
Groups
Create/join groups with roles (admin, moderator, member) and privacy levels
Direct messaging
1:1 conversations with message history and read receipts
Notifications
Notify users of friend requests, likes, comments, tags, and messages
Search
Search users by name
Before diving into code, clarify the use cases and edge cases. Understanding the problem deeply leads to better class design.
Identify the primary actions users will perform. For a parking lot: park vehicle, exit vehicle, check availability. Each becomes a method.
Who interacts with the system? Customers, admins, automated systems? Each actor type may need different interfaces.
What are the limits? Max vehicles, supported vehicle types, payment methods. Constraints drive your data structures.
What happens on overflow? Concurrent access? Payment failures? Thinking about edge cases reveals hidden complexity.
The complete explanation is included with Career and All Access. Compare it with your approach once you’ve worked through the problem.