Information Technology
iOS Developer Interview Questions and Answers
iOS developers design and build applications for Apple's mobile ecosystem using Swift and UIKit/SwiftUI. They create seamless, performant, and visually engaging user experiences, leveraging Apple's human interface guidelines and modern APIs.
20 practice questions with explanations and sample answers.
1. Why do you want to develop for iOS?
What the interviewer is looking for
Show passion for Apple's ecosystem and user experience.
Sample answer
I love the polish and attention to detail in iOS apps. Developing for iOS means working with elegant APIs and a passionate user base.
2. Explain the differences between Swift and Objective‑C.
What the interviewer is looking for
Highlight Swift's safety, modern features, and interoperability.
Sample answer
Swift is modern, safe, and concise, with features like optionals and type inference. Objective‑C is older but still interoperates with Swift in mixed codebases.
3. What is the delegate pattern and how do you use it?
What the interviewer is looking for
Define delegation as a design pattern for communication.
Sample answer
Delegation allows one object to communicate with another via a protocol. I use it for UITableView events and custom view communication.
4. Describe your experience with auto layout and interface builder.
What the interviewer is looking for
Show proficiency in creating responsive layouts.
Sample answer
I use auto layout with constraints and stack views to create adaptive UIs for all screen sizes.
5. How do you manage memory in Swift (ARC, retain cycles)?
What the interviewer is looking for
Explain ARC and weak references to break cycles.
Sample answer
I use Automatic Reference Counting and break retain cycles with weak or unowned references in closures and delegates.
6. What is your experience with SwiftUI compared to UIKit?
What the interviewer is looking for
Discuss declarative vs imperative approaches.
Sample answer
I have used both. SwiftUI is declarative and faster for prototyping, while UIKit offers more granular control.
7. How do you handle asynchronous operations (URLSession, Combine)?
What the interviewer is looking for
Use async/await or Combine for reactive programming.
Sample answer
I use async/await for network calls and Combine for reactive patterns and data binding.
8. Describe a time you optimised an iOS app's performance.
What the interviewer is looking for
Show profiling and improvements.
Sample answer
I used Instruments to identify and fix a memory leak, and optimised image loading with caching, resulting in smoother scrolling.
9. What architectural patterns have you used (MVC, MVVM, VIPER)?
What the interviewer is looking for
Explain your preferred pattern and its benefits.
Sample answer
I prefer MVVM with Combine for data binding, as it separates UI logic from business logic and improves testability.
10. How do you test iOS applications (unit and UI)?
What the interviewer is looking for
Use XCTest for unit tests and XCUITest for UI tests.
Sample answer
I write unit tests with XCTest and UI tests with XCUITest to ensure reliability.
11. What is your experience with Core Data or other persistence frameworks?
What the interviewer is looking for
Discuss Core Data, Realm, or UserDefaults.
Sample answer
I have used Core Data for complex data models and Realm for simpler, real‑time data needs.
12. How do you handle dependency injection in iOS?
What the interviewer is looking for
Use initialiser injection or SwiftUI's environment.
Sample answer
I use initialiser injection for view models and, in SwiftUI, environment objects for shared state.
13. What is the role of the App Delegate and Scene Delegate?
What the interviewer is looking for
Explain lifecycle management.
Sample answer
AppDelegate handles app‑level events, while SceneDelegate manages individual windows or scenes in iOS 13+.
14. Describe a time you handled a tricky UI challenge.
What the interviewer is looking for
Show creativity and problem‑solving.
Sample answer
I implemented a custom collection view layout for a gallery, using a custom flow layout to achieve the desired staggered look.
15. What are some common security practices in iOS development?
What the interviewer is looking for
Data encryption, keychain, and secure networking.
Sample answer
I use the Keychain for sensitive data, enforce HTTPS, and implement certificate pinning for extra security.
16. How do you keep up with new iOS releases and frameworks?
What the interviewer is looking for
Read Apple's documentation, watch WWDC sessions.
Sample answer
I watch WWDC sessions, read Apple's Human Interface Guidelines, and follow iOS developer blogs.
17. Describe your experience with push notifications (APNs).
What the interviewer is looking for
Configure APNs and handle notifications.
Sample answer
I have integrated APNs using Firebase Cloud Messaging and handled both remote and local notifications.
18. How do you handle app state restoration?
What the interviewer is looking for
Use state restoration APIs or save state in UserDefaults.
Sample answer
I use NSUserActivity or preserve UI state via the restoration identifier to provide a seamless experience.
19. What is the importance of accessibility in iOS development?
What the interviewer is looking for
Use VoiceOver and dynamic type.
Sample answer
I ensure accessibility by adding accessibility labels, supporting dynamic type, and testing with VoiceOver.
20. Why do you want to work for our mobile team?
What the interviewer is looking for
Mention their app or user base.
Sample answer
Your app has a great reputation, and I want to contribute to its continued innovation.