iOS Developer Interview Questions UK: 8 Real Questions and What Interviewers Want

Applying for a iOS Developer job in the UK? Here is what you are likely to be asked. These questions come from our iOS Developer question bank of 16 questions, written for UK employers at mid-level level.

Eight iOS Developer interview questions, and what the interviewer is thinking

1. How does memory management work in Swift, and how do you avoid retain cycles with closures?

Why they ask: ARC and retain cycles are one of the most commonly tested iOS topics.

2. What are the differences between SwiftUI and UIKit, and how would you decide which to use in a project?

Why they ask: Most iOS teams now mix the two, so they want balanced judgement.

3. How does Swift concurrency work with async/await, actors and the main actor, and how does it compare with GCD?

Why they ask: Modern iOS codebases use Swift concurrency, and data races are a real risk.

4. How do you structure an iOS app, and what are the pros and cons of MVC, MVVM and architectures such as TCA or VIPER?

Why they ask: Architecture knowledge shows you can build maintainable apps.

5. How do you persist data on iOS, and when would you use Core Data, SwiftData, UserDefaults or the Keychain?

Why they ask: Storage choices affect security, reliability and performance.

6. App Review rejects your update because of a privacy issue with how you describe data collection. What do you do?

Why they ask: Store compliance issues are routine, and they want calm, thorough handling.

7. Tell me about a time you built or significantly improved an iOS feature and what the result was.

Why they ask: They want evidence of delivery and impact in iOS work specifically.

8. Why do you want to be an iOS developer, and how do you keep up with Apple's yearly platform changes?

Why they ask: They want enthusiasm for the platform and a continuous learning habit.

A sample answer to question 1

How does memory management work in Swift, and how do you avoid retain cycles with closures?

Swift uses Automatic Reference Counting. Each class instance has a count of strong references, and it's deallocated when the count reaches zero. Value types such as structs and enums are copied rather than reference counted, which is one reason I favour them for models. A retain cycle occurs when two objects hold strong references to each other, or when an object stores a closure that captures self strongly. That means neither is released and memory leaks. I break cycles with weak or unowned references. Weak is optional and becomes nil when the object is deallocated, so it suits delegates and closures where self might disappear, while unowned assumes the object outlives the reference and crashes if not. In closures I use a weak self capture list and then guard let self, particularly for escaping closures like network callbacks, timers or Combine sinks. I check for leaks using the Debug Memory Graph and Instruments' Leaks tool, and add deinit logging when investigating suspect view controllers.

Common mistake to avoid: Using unowned without certainty; Not mentioning how to detect leaks

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the iOS Developer interview questions page. The first five are free, no sign-up needed.