iOS Engineer Interview Guide

iOS and Swift Interview Questions

Evaluate iOS engineers on Swift, SwiftUI, concurrency, lifecycle, and production discipline for App Store releases.

Strong iOS candidates reason about memory, concurrency, lifecycle, and shipping discipline. These prompts focus on practical Swift judgment, not API trivia.

Book A Demo
Section 1

Swift

Check value vs reference semantics, optionals, and protocol-oriented design.

1. When would you pick a struct over a class in Swift, and vice versa?

Interview prompt

Strong signal

Discusses value semantics, identity, mutation, and SwiftUI integration.

Follow-up probes

  • •What about reference cycles?
  • •How does this affect testability?

Red flags

  • •Says structs are always better.
  • •Cannot explain copy-on-write.
Section 2

Concurrency

Evaluate Swift Concurrency, actors, and cancellation.

1. How would you migrate a callback-based networking layer to async/await?

Interview prompt

Strong signal

Discusses continuations, cancellation, error propagation, and structured concurrency.

Follow-up probes

  • •How do you handle cancellation across tasks?
  • •When do you use actors?

Red flags

  • •Mixes DispatchQueue and async without reason.
  • •Ignores cancellation.
Section 3

SwiftUI

Test view lifecycle, state ownership, and performance.

1. A SwiftUI list re-renders on every keystroke and feels slow. How would you diagnose it?

Interview prompt

Strong signal

Reasons about state ownership, identity, equatable views, and Instruments tooling.

Follow-up probes

  • •What about EnvironmentObject overuse?
  • •When would you drop to UIKit?

Red flags

  • •Adds @State everywhere.
  • •No profiling tool mentioned.

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