iOS Developer Interview Questions - Swift & Objective-C

Introduction

Hiring the right iOS Developer (Swift/Objective-C) is critical for Information Technology teams building robust, user-centered mobile applications. The right candidate delivers secure, maintainable code and a smooth user experience across iPhone and iPad devices.

This guide provides a structured set of role-specific interview prompts, from basic conceptual checks to advanced architecture and optimization questions. It also includes pre-screening one-way video interview questions ideal for efficient candidate evaluation.

iOS Developer (Swift/Objective-C) Interview Questions

Basic iOS Developer (Swift/Objective-C) Interview Questions

• Explain the main differences between Swift and Objective-C. When would you choose one over the other?
• What are optionals in Swift and how do you handle them safely?
• Describe Automatic Reference Counting and how retain cycles occur in iOS apps.
• What is the Model-View-Controller pattern and how is it applied in Cocoa Touch?
• How do delegates and protocols work in iOS? Give a simple use case.
• What is the purpose of Grand Central Dispatch and how do you use it for concurrency?
• Explain the iOS app lifecycle and how you respond to state transitions like backgrounding.
• How do you update the UI from a background thread and why must you be careful?

Intermediate iOS Developer (Swift/Objective-C) Interview Questions

• Describe how you would implement dynamic table view cells that adjust height based on content.
• Explain a strategy for fetching remote JSON data, parsing it, and updating the UI with error handling and retries.
• How do you migrate a Core Data model without losing user data? Describe lightweight migration.
• Compare using URLSession with third-party networking libraries. What are trade offs for maintainability and performance?
• Show how you would debug and fix a memory leak using Instruments. What specific tools or traces would you inspect?
• Describe an approach to implement offline support and data synchronization when connectivity is intermittent.
• How do you write unit tests and UI tests for iOS code? Provide an example of a meaningful unit test.
• Explain how to integrate push notifications and handle user actions from notification responses.
• How do you manage dependencies and third-party frameworks in an iOS project?
• Describe how you would implement accessibility improvements to make an app usable for VoiceOver users.

Advanced iOS Developer (Swift/Objective-C) Interview Questions

• Design an offline-first sync architecture for an app that must support conflict resolution across devices.
• Explain protocol-oriented programming and how you would apply it to reduce coupling in a large codebase.
• How would you structure a modular iOS app to reduce build times and improve team parallelism?
• Describe techniques to optimize app launch time and measure improvements.
• How do you secure sensitive user data locally and in transit? Discuss keychain, CommonCrypto, and TLS best practices.
• Walk through diagnosing a CPU spike in a production app. What profiling steps do you take and how do you identify root causes?
• How would you design a feature flag system for incremental rollouts and A B testing in mobile apps?
• Discuss strategies for reducing app size and managing asset catalogs and on demand resources.
• Explain continuous integration and continuous delivery practices for iOS, including code signing and automated testing.
• How do you mentor junior engineers and lead code reviews to improve quality while maintaining development velocity?

Pre-Screening Video Interview Questions for iOS Developer (Swift/Objective-C)

These questions are ideal for one-way video interviews and pre-screening interviews on ScreeningHive. They help hiring teams quickly evaluate technical knowledge, communication skills, and cultural fit before moving to live interviews.

1. Describe a recent iOS feature you implemented and the main technical challenges you faced.

   This question evaluates practical experience, problem solving, and the candidate's ability to explain technical work clearly.

2. How do you decide between using Swift or Objective-C when joining an existing codebase?

   This assesses judgment about language interoperability, migration risk, and long term maintenance considerations.

3. Give an example of a performance issue you resolved and the measurable impact of your fix.

   Evaluates debugging skills, use of profiling tools, and focus on measurable outcomes.

4. Explain a time you improved app reliability or reduced crash rates. What steps did you take?

   This reveals practices around telemetry, crash analysis, testing, and preventive measures.

5. How do you approach working with product managers and designers to deliver a feature on time?

   This measures collaboration, communication, and the ability to balance technical and business priorities.

Conclusion

These iOS Developer (Swift/Objective-C) interview questions provide hiring managers, recruiters, and candidates with a practical roadmap for technical evaluation. The mix of basic, intermediate, and advanced prompts helps surface skill level, problem solving, and architectural judgment.

Using ScreeningHive one-way video interviews supports faster screening, consistent evaluations, and improved hiring efficiency by capturing candidate responses on demand. Incorporating these role-specific questions into pre-screening interview questions helps teams focus live interview time on deeper technical fit.