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
0 / 10 completed
1 / 10
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 / 10
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 / 10
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 / 10
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 / 10
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.
6 / 10
Sarah (Senior iOS Engineer) comments on your pull request: 'This section of the code uses a lot of string concatenation. Consider using NSString's formatting methods for improved performance and readability.' Which of the following responses best addresses Sarah's feedback in a professional manner?
The core issue here isn't just accepting or rejecting a suggestion – it's demonstrating willingness to learn and improve your practices. Option A is dismissive and unprofessional. Option B seeks guidance constructively. Option C ignores valid feedback. Option D shows you are open to incorporating best practices; this demonstrates a proactive approach to development, crucial for collaboration.
7 / 10
You're in a Slack channel discussing a bug report. Another engineer, David, asks: 'What's the best way to handle nil values when accessing data from an API?' Which of the following responses is most appropriate for your reply?
Handling `nil` values is critical in iOS development, especially when dealing with external APIs. Option A is overly simplistic and doesn't address potential crashes. Option B correctly utilizes Swift's safe operators for robust nil handling. Options C and D are inappropriate responses to a technical question about data access.
8 / 10
As the lead developer on a new feature, you're writing the PR description for your team. Which of the following descriptions best communicates the changes you've made to a complex data model?
A good PR description needs to be clear, concise, and informative. Option A is vague and doesn't provide enough detail. Option B specifically outlines the changes made to the code, including the class name and added properties – this is crucial for maintainability and understanding. Options C and D focus on broader aspects rather than specific code modifications.
9 / 10
During a daily standup meeting, your manager asks: 'What progress did you make yesterday on the onboarding flow?' You respond: 'I finished implementing the user authentication and data validation steps, but I'm still struggling with integrating it into the existing navigation structure.' Which of the following statements best reflects your situation?
Honest and transparent communication is vital in standups. Option A overstates your accomplishments. Option B deflects from the actual issue. Option C accurately describes the situation – acknowledging challenges and seeking support is a key skill. Option D avoids responsibility.
10 / 10
The App Store rejected your latest update due to 'incorrect data validation.' You need to quickly address this and submit a new build. What's the most efficient approach?
Responding effectively to App Store rejections is crucial for maintaining a positive relationship with Apple. Option A demonstrates a lack of urgency and responsibility. Option B outlines the standard process – fixing the issue, testing, and resubmitting. Options C and D are less effective strategies than directly addressing the rejection.
What does "iOS Engineer Interview Questions | Coders Lingo" cover?
Practise professional English for iOS engineering interviews: Swift memory management, UITableView performance, background tasks, and App Store processes.
How many questions are in this interview set?
This set has 10 exercises, each with a full explanation.
Is this exercise free to use?
Yes. Every exercise on CoderSlingo, including this one, is free to use with no account, sign-up, or paywall.
Do these exercises include model answers?
Yes. Each interview question gives you several possible responses and asks you to pick the one that communicates most clearly and completely — the explanation then breaks down exactly why that answer works, including the specific vocabulary a strong candidate would use.
What if I choose an answer that isn't the strongest one?
You'll see which option was correct and read a full explanation of why it's stronger than the alternatives, plus the key vocabulary and phrasing worth reusing in a real interview.
Can I retry the questions?
Yes — use the "Try again" button on the results screen to reset and go through the set again.
Is this the same as a real technical or behavioural interview?
No — it's focused practice for the language side of interviewing: recognising which phrasing sounds precise and confident versus vague, and knowing the vocabulary interviewers expect for this role. It won't replace mock interviews, but it builds the vocabulary you'll need in one.
Where can I find interview prep for other roles?
Browse the full Interview exercises hub for 170+ modules covering behavioural, technical, and system design rounds across dozens of IT roles, or check the "Next up" link below to continue.
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Who writes these interview questions?
Every question is written by the CoderSlingo team based on real technical interview patterns for this role, then reviewed for accuracy and clarity.