└── README.md


/README.md:
--------------------------------------------------------------------------------
  1 | # 🚀 Company-Wise iOS Technical Interview Questions  
  2 | 
  3 | <p align="center">
  4 |   <a href="https://www.linkedin.com/in/shobhakar-tiwari/">Prepared By: Shobhakar Tiwari</a>
  5 | </p>
  6 | 
  7 | - 🎓 Welcome, I’m Shobhakar Tiwari working in the USA 🇺🇸 and currently in the Central Standard Time Zone (CST).  I enjoy writing blogs on Medium, contributing to the iOS dev community, and sharing iOS interview questions to support junior and senior iOS developers alike.
  8 |   
  9 | - [If you preparing for iOS Interview feel free to connect for mentorship.](https://www.linkedin.com/in/shobhakar-tiwari/)
 10 | 
 11 | - A comprehensive collection of real-world technical interview questions and scenarios from leading technology companies. This repository helps developers prepare for coding rounds, system design interviews, and technical assessments.
 12 | 
 13 | ## **Walmart Mock Interview Question**
 14 | - [Walmart Interview Question](#walmart-interview-question)
 15 |   - [Problem Statement](#problem-statement)
 16 |   - [Technical Requirements](#technical-requirements)
 17 |   - [Implementation Guide](#implementation-guide)
 18 |   - [Code Solution](#code-solution)
 19 |   - [Technical Deep Dive](#technical-deep-dive)
 20 | 
 21 | ### Problem Statement
 22 | **Real-time ETA Tracking in Ride-Sharing Application**
 23 | 
 24 | Design and implement a feature for a ride-sharing application that displays real-time ETA (Estimated Time of Arrival) updates for drivers. The system must efficiently handle periodic network requests while maintaining optimal resource usage and user experience.
 25 | 
 26 | ### Technical Requirements
 27 | 1. Implement periodic ETA fetching (10-second intervals)
 28 | 2. Handle view lifecycle management
 29 | 3. Implement proper network request management
 30 | 4. Ensure thread-safe UI updates
 31 | 5. Implement memory leak prevention
 32 | 6. Handle error cases and network failures
 33 | 
 34 | ### Implementation Guide
 35 | 
 36 | #### Architecture Components
 37 | - **Timer System**: Manages periodic network requests
 38 | - **Network Layer**: Handles API communication
 39 | - **UI Layer**: Updates and manages view state
 40 | - **Error Handling**: Implements retry mechanism with exponential backoff
 41 | 
 42 | #### Key Considerations
 43 | - Resource optimization during screen transitions
 44 | - Thread safety in UI updates
 45 | - Memory management
 46 | - Network failure resilience
 47 | 
 48 | ### Code Solution
 49 | 
 50 | ```swift
 51 | import UIKit
 52 | 
 53 | class ETAViewController: UIViewController {
 54 |     // MARK: - Properties
 55 |     private var timer: Timer?
 56 |     private let etaURL = URL(string: "https://api.example.com/driver/eta")!
 57 |     
 58 |     // MARK: - Lifecycle Methods
 59 |     override func viewWillAppear(_ animated: Bool) {
 60 |         super.viewWillAppear(animated)
 61 |         startFetchingETA()
 62 |     }
 63 |     
 64 |     override func viewWillDisappear(_ animated: Bool) {
 65 |         super.viewWillDisappear(animated)
 66 |         stopFetchingETA()
 67 |     }
 68 |     
 69 |     // MARK: - Private Methods
 70 |     private func startFetchingETA() {
 71 |         timer = Timer.scheduledTimer(
 72 |             timeInterval: 10.0,
 73 |             target: self,
 74 |             selector: #selector(fetchETA),
 75 |             userInfo: nil,
 76 |             repeats: true
 77 |         )
 78 |         timer?.fire()
 79 |     }
 80 |     
 81 |     private func stopFetchingETA() {
 82 |         timer?.invalidate()
 83 |         timer = nil
 84 |     }
 85 |     
 86 |     @objc private func fetchETA() {
 87 |         let task = URLSession.shared.dataTask(with: etaURL) { [weak self] data, response, error in
 88 |             guard let self = self else { return }
 89 |             
 90 |             if let error = error {
 91 |                 print("Failed to fetch ETA: \(error)")
 92 |                 return
 93 |             }
 94 |             
 95 |             guard let data = data else { return }
 96 |             if let eta = self.parseETA(from: data) {
 97 |                 DispatchQueue.main.async {
 98 |                     self.updateUI(with: eta)
 99 |                 }
100 |             }
101 |         }
102 |         task.resume()
103 |     }
104 |     
105 |     private func parseETA(from data: Data) -> String? {
106 |         return String(data: data, encoding: .utf8)
107 |     }
108 |     
109 |     private func updateUI(with eta: String) {
110 |         print("ETA Updated: \(eta)")
111 |     }
112 | }
113 | ```
114 | 
115 | ### Technical Deep Dive
116 | 
117 | #### 1. Network Failure Handling
118 | Implement an exponential backoff strategy for handling network failures:
119 | 
120 | ```swift
121 | private func retryRequest(after delay: TimeInterval) {
122 |     DispatchQueue.main.asyncAfter(deadline: .now() + delay) { [weak self] in
123 |         self?.fetchETA()
124 |     }
125 | }
126 | ```
127 | 
128 | #### 2. Thread Safety Implementation
129 | Ensure UI updates occur on the main thread:
130 | 
131 | ```swift
132 | DispatchQueue.main.async {
133 |     self.updateUI(with: eta)
134 | }
135 | ```
136 | 
137 | #### 3. Request Cancellation
138 | Implement proper request cancellation to prevent resource leaks:
139 | 
140 | ```swift
141 | private var currentTask: URLSessionDataTask?
142 | 
143 | @objc private func fetchETA() {
144 |     currentTask?.cancel()
145 |     currentTask = URLSession.shared.dataTask(with: etaURL) { [weak self] data, response, error in
146 |         // Handle response
147 |     }
148 |     currentTask?.resume()
149 | }
150 | ```
151 | 
152 | ## Contributing
153 | We welcome contributions! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.
154 | 
155 | ## All rights @Shobhakar Tiwari
156 | 


--------------------------------------------------------------------------------