How does Swift's Dictionary work under the hood?
Walk through Swift Dictionary as a CoW hash table — hashing invariants, collisions, complexity traps, nil removal, ordering, concurrency, and key design for senior interviews
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iOS interview questions
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How would you demonstrate Copy-on-Write behavior with a custom struct?
Demonstrate Copy-on-Write with a value-typed linked list that shares storage on assignment and copies it only when a mutation occurs using isKnownUniquelyReferenced.
What's the difference between strong, weak, and unowned references?
Under ARC, strong keeps an object alive, unowned tracks a direct non-owning pointer that must outlive use, and weak goes through a side table so access can become nil after deinit
When would you choose a Swift actor over a serial DispatchQueue?
Compare language-level isolation with traditional queue-based synchronization in production iOS code
Which design patterns have you used in iOS, and what tradeoffs did they have?
Group design patterns into creational, structural, and behavioral, then explain real iOS examples from SDKs and your own implementation experience with the tradeoffs that matter in production
How does struct memory layout work in Swift?
Explain MemoryLayout, padding, alignment, and stride; show why stored-property order changes a struct's footprint; and connect it to arrays, performance, and low-level interop