iOS Engineer mock interview questions
19 questions a iOS Engineer panel actually asks, with what each one tests and what a strong answer contains, then practice any of them live. Swift, memory and app architecture rounds for iOS engineer interviews.
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A question a iOS Engineer panel actually asks, answered out loud, scored on what you said and how you said it. Under two minutes, and nothing to sign up for.
“A view controller is never deallocated after the user leaves the screen. How do you find out why, and what are the usual causes?”
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19 ios engineer mock interview questions
The questions a iOS Engineer panel actually asks, with what each one is testing and what a strong answer contains. Click any question to run it in a live session: your AI interviewer will cover it and score how you answer.
- 1.
A view controller is never deallocated after the user leaves the screen. How do you find out why, and what are the usual causes?
Why they ask it: Retain cycles are the classic iOS memory bug. The interviewer wants to see both the tooling and a clear model of ARC.
A strong answer: Confirm with a deinit log or the memory graph debugger in Xcode, which shows what is holding the reference. Usual causes: a closure capturing self strongly and stored by self or by something self owns, a delegate declared strong instead of weak, a timer or notification observer retaining its target, and a Combine subscription stored without breaking the cycle. Fix with weak or unowned captures chosen deliberately, and explain when unowned is unsafe.
- 2.
How does Swift concurrency change how you write networking code, and what does @MainActor guarantee?
Why they ask it: Modern iOS codebases are moving to async/await and actors. This tests whether you understand isolation, not just syntax.
A strong answer: async/await replaces completion handler pyramids with structured code, tasks carry cancellation that the code should check, and actors protect mutable state from data races. @MainActor isolates code to the main actor so UI updates happen on the main thread and the compiler enforces that at call sites. Mention that a Task started from a view needs cancelling when the view goes away and that stricter concurrency checking surfaces Sendable issues.
- 3.
In SwiftUI, a list resets its scroll position and loses state whenever the parent view updates. What might be going on?
Why they ask it: SwiftUI identity and state ownership are the most common sources of confusing bugs. This checks whether you understand how views are recreated.
A strong answer: View structs are recreated often, so state must be owned correctly: @State for local value state, @StateObject or the Observable macro with @State for a model the view owns, and @ObservedObject only for models passed in. Unstable identity, such as ids generated on each render or a conditional that swaps view types, makes SwiftUI treat the view as new and discard its state. Stable identifiers fix the list.
- 4.
Build a screen that fetches a list of items from an API, shows loading and error states, and supports pull to refresh.
Why they ask it: The standard practical exercise. It shows how you structure a feature and handle real-world states, not only the happy path.
A strong answer: A model layer decoding with Codable, a view model or observable object exposing a single state enum of loading, loaded and failed, networking behind a protocol so it can be faked in tests, cancellation of in-flight requests on refresh, and attention to empty states, accessibility labels and Dynamic Type.
- 5.
You get a crash report from production that you cannot reproduce. What do you do?
Why they ask it: Crash triage is routine iOS work. The interviewer wants to hear about symbolication and reasoning from evidence.
A strong answer: Make sure the report is symbolicated with the right dSYM, read the crashing thread and exception type, check device, OS version and app version patterns in the crash reporting tool, look at the code path for force unwraps, out of range indexes or threading issues, add logging or breadcrumbs if the cause is unclear, and ship a fix with a regression test where possible.
- 6.
How do you choose an architecture for a new iOS app, and what goes wrong with a massive view controller?
Why they ask it: Architecture questions test judgment rather than loyalty to one pattern.
A strong answer: Keep views thin and move logic into testable types, whether MVVM, a coordinator for navigation, or another pattern the team knows. Choose based on team size, testability and the UI framework. A massive view controller mixes networking, formatting and navigation, which makes it hard to test and change. Avoid adding layers the app does not need.
- 7.
Tell me about a release that went badly, for example an App Store rejection or a bug that reached users. How did you handle it?
Why they ask it: Mobile releases cannot be rolled back instantly, so the interviewer wants to see caution and recovery skills.
A strong answer: The situation, how it was detected, the immediate mitigation such as a server-side feature flag or an expedited review, the fix, and what changed afterwards such as phased releases, better test coverage or a release checklist.
How the iOS Engineer interview runs
Usually a recruiter screen, then a technical round with an iOS engineer on Swift and UIKit or SwiftUI fundamentals: memory management, concurrency and view lifecycle. Most loops include either a take-home app or a live pairing session building a screen that loads data from an API into a list. Later rounds cover app architecture, a debugging or crash scenario, and how you work with designers and handle App Store releases.
What the panel scores
Swift and memory
Whether you understand ARC, value types and Swift language features.
- Diagnoses retain cycles with tooling
- Chooses weak versus unowned deliberately
- Uses value types and optionals safely
Concurrency and UI correctness
Whether UI code is thread safe and responsive.
- Understands actor isolation and @MainActor
- Handles task cancellation
- Knows SwiftUI state ownership and identity
App architecture
Whether the app stays maintainable as it grows.
- Keeps views thin and logic testable
- Chooses patterns based on the team and app
- Handles loading, error and empty states
Release and quality
Whether you ship stable apps to users.
- Symbolicates and triages crashes
- Uses phased releases and feature flags
- Writes tests for fixed bugs
Common questions in every interview
These come up in almost every iOS Engineer interview regardless of the company or the round.
- 8.
Tell me about yourself.
Why they ask it: Opens the interview and sets the frame. The interviewer is checking whether you can select what matters for this job rather than narrate your whole history.
A strong answer: A 60-90 second arc: where you are now, one or two proof points that match the posting, and why this role is the logical next step. Present, past, then future.
- 9.
Why do you want this role?
Why they ask it: Tests whether you read the job description or mass-applied. Weak answers are about what the candidate gets; strong answers connect to the work itself.
A strong answer: Two specifics from the posting or the company's actual work, plus an honest line about what you want to get better at here.
- 10.
Walk me through your resume.
Why they ask it: Checks that your story holds together and that the transitions were deliberate rather than accidental.
A strong answer: Chronological but fast, with a reason attached to each move and more time on the roles closest to this one.
- 11.
Tell me about a time you failed.
Why they ask it: Tests self-awareness and whether you own outcomes. Interviewers are listening for a real failure, not a disguised strength.
A strong answer: A genuine miss, what you specifically got wrong, the cost, and the concrete thing you changed afterwards that has since held up.
- 12.
Tell me about a conflict with a coworker or manager.
Why they ask it: Predicts how you behave when the team disagrees. The trap is blaming the other person.
A strong answer: The substance of the disagreement, what you did to understand their position, how it resolved, and what the working relationship looked like after.
- 13.
What's your greatest strength?
Why they ask it: Checks whether you know what you're actually good at and can prove it.
A strong answer: One strength that maps to the posting, plus a short example where it produced a measurable result.
- 14.
What's your greatest weakness?
Why they ask it: Tests honesty and whether you're actively working on something. Rehearsed non-answers ('I work too hard') read as evasive.
A strong answer: A real limitation that isn't core to the job, the system you built to manage it, and evidence it's improving.
- 15.
Tell me about a time you had to influence someone without authority.
Why they ask it: Almost every role depends on getting people who don't report to you to change course.
A strong answer: What you wanted, why they resisted, the evidence or framing that moved them, and what actually shipped as a result.
- 16.
Where do you see yourself in five years?
Why they ask it: Tests whether this job fits your trajectory, which is a retention question in disguise.
A strong answer: A direction rather than a title, and a line about the skills this role would build toward it. Vague ambition and rigid title-chasing both land badly.
- 17.
Why are you leaving your current job?
Why they ask it: Screens for red flags. Interviewers listen for how you talk about people you no longer work with.
A strong answer: Forward-looking and specific about what you're moving toward. Criticism of a former employer costs you more than it gains, even when it's deserved.
- 18.
What are your salary expectations?
Why they ask it: Checks whether you've done market research and whether you're in range before anyone spends more time.
A strong answer: A researched range with your target near the bottom of it, framed against the scope of the role. Deflect once if the posting has no band, then answer.
- 19.
Do you have any questions for us?
Why they ask it: The most under-prepared question in the interview, and the one that most changes the final impression.
A strong answer: Two or three questions about how the team actually works: what the first 90 days look like, how success is measured, what the hardest part of the job is.
Every round ends in a scorecard like this
Your iOS Engineer answers, quoted back, scored on what this role is judged on, with the line to say instead.
Real screen from the app. Sample from a product design round.
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Questions & answers
- Is the iOS Engineer mock interview free?
- Yes. 30 voice minutes and unlimited typed iOS Engineer interviews, no card. You get the complete rubric scorecard every time, with the evidence quoted from your own answers. Nothing is blurred.
- Can I use my own job description instead?
- Yes. Predefined roles are starting points. Paste any JD in the setup form and your AI interviewer will tailor questions to that posting.
- How is scoring tailored to this role?
- We pre-fill a realistic iOS Engineer job description and interview format so questions and the scorecard match how this role is actually interviewed.
- Should I tailor my resume before practicing?
- Run a resume fit check against a iOS Engineer job description first, then practice the interview with the same JD for a tighter loop.