A hiring manager's question bank for iOS developers — Swift, ARC and retain cycles, the view controller lifecycle, SwiftUI, and modern concurrency. Built to separate people who can lay out a screen from people who ship stable, memory-clean apps to the App Store.
Interviewing an iOS developer well means going past whether they can build a screen and into whether they understand Apple's runtime, memory model, and UI paradigms. The single most revealing iOS topic is memory management: iOS uses automatic reference counting, not a garbage collector, so a candidate must genuinely understand strong, weak, and unowned references and be able to explain how a retain cycle forms — a view controller holding a closure that captures self strongly is the classic leak, and someone who cannot spot it will ship apps that balloon in memory. Beyond ARC, you want fluency in Swift itself: optionals and safe unwrapping, value versus reference semantics with structs and classes, protocols and protocol-oriented design, and generics. The UI story is in transition, so strong candidates can work in both UIKit — with its view controller lifecycle and delegate patterns — and SwiftUI's declarative, state-driven model, and can explain the tradeoffs. Concurrency has modernized too: async/await and actors have largely replaced manual GCD juggling, and you want to hear that a candidate keeps work off the main thread without introducing data races. The questions below move from Swift fundamentals through memory and the lifecycle into UI, concurrency, and architecture. Pair a couple of Swift questions with one retain-cycle discussion and one "your app is slow or leaking" scenario, and you will quickly tell whether someone has shipped and maintained a real iOS app.
Choose six to eight questions across two or three categories rather than the entire list. Open with a Swift fundamentals question, then spend real time on a Memory & ARC scenario — the retain-cycle question alone tells you a lot — and one UI or concurrency discussion. Push every clean answer with "where would a retain cycle form here?" or "which thread does that run on?" to see real depth.
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