Practise answering common interview questions for iOS engineering roles, covering Swift, UIKit, performance, testing, and App Store deployment.
Interview tips
Use STAR method for behavioural questions
Profile before optimising — mention specific tools (Instruments)
Show knowledge of both UIKit and SwiftUI when relevant
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1 / 5
An interviewer asks: "How do you manage memory in a Swift application to avoid retain cycles?" — which response is most professional?
The best answer demonstrates concrete knowledge: weak vs unowned references, the specific [weak self] capture list pattern with nil-guarding, delegate declaration patterns, and practical use of Instruments for detecting leaks in production. It shows that the candidate understands ARC while knowing where it does not automatically protect you. The other responses either incorrectly claim ARC prevents all retain cycles, avoid the problem rather than solving it, or conflate deallocation with cycle prevention.
2 / 5
An interviewer asks: "How do you approach performance optimisation for a slow UITableView?" — which response is most professional?
The best answer follows the professional engineering approach: profile before optimising, identify specific root causes, then apply targeted fixes. It demonstrates knowledge of specific iOS performance issues: cell reuse, main-thread layout, image decoding, and offscreen rendering. The mention of specific tools (Instruments, Time Profiler, Core Animation template) shows practical experience. The other responses are valid tactics but apply them without profiling first, which may miss the actual bottleneck.
3 / 5
An interviewer asks: "How do you handle background tasks in iOS to ensure they complete even when the app is backgrounded?" — which response is most professional?
The best answer correctly distinguishes between three different iOS background execution mechanisms appropriate for different use cases: beginBackgroundTask for short extensions, URLSession background configuration for network tasks, and BGTaskScheduler for periodic work. This specificity demonstrates real iOS experience. The other responses confuse background threading (DispatchQueue) with background app execution, describe workarounds rather than solutions, or misuse push notifications as a task mechanism.
4 / 5
An interviewer asks: "How do you test a view model in a Swift iOS application?" — which response is most professional?
The best answer describes a complete unit testing approach: dependency injection for testability, protocol-based mocking, handling async code in tests, and validating both success and error paths. It also shows modern Swift testing knowledge (async/await, Combine). The other responses either avoid unit testing in favour of manual or UI testing, or surrender to the (incorrect) view that view models are hard to test — which is precisely what dependency injection solves.
5 / 5
An interviewer asks: "How do you handle App Store review delays when you need to ship a critical bug fix?" — which response is most professional?
The best answer demonstrates multi-layered thinking: using expedited review for genuine emergencies, feature flags for server-side mitigation, proactive monitoring to catch issues early, and phased releases to limit impact. It shows professional judgement about when each tool is appropriate. The other responses are either passive (just wait), violate App Store guidelines (JavaScript bridges for logic updates can result in rejection), or treat user communication as a solution rather than a complement to a technical fix.