Apple Swift Interview Questions 2026
Published July 22, 2026 · Updated July 22, 2026
5 real Swift interview questions asked at Apple. Upvoted by engineers who cleared the loop. Covers Technical rounds.
5 questions
133 engineers asked
256 upvotes
Company: Apple
Technology: Swift
All Swift Questions Asked at Apple
Apple
Medium
Technical round
SwiftiOS
Explain how ARC (Automatic Reference Counting) works in Swift/Objective-C.
What is a retain cycle and how do you break one? Give an example using a delegate pattern and explain when to use weak vs unowned references.
↑ 91 upvotes · 34 engineers asked this · SDE1
Apple
Hard
Technical round
SwiftiOSKotlin
Explain iOS memory management: ARC, strong/weak/unowned references, retain cycles. How does the system handle memory pressure? Walk through what happens when an app receives a memory warning and is then terminated.
↑ 62 upvotes · 39 engineers asked this · SDE2
Apple
Medium
Technical round
SwiftJavaPython
Given a BST, find the closest value to a given target. Explain the O(log n) iterative approach using BST properties, and how the answer changes if the tree is unbalanced.
↑ 41 upvotes · 24 engineers asked this · SDE1
Apple
Medium
Technical round
SwiftiOS
How does Core Data work in iOS? Explain the managed object context, persistent store coordinator, and the fetch request pipeline. When would you use Core Data vs Realm vs SQLite directly?
↑ 43 upvotes · 26 engineers asked this · SDE2
Apple
Medium
Technical round
2-6 yearsSwift
In Swift, what is the difference between DispatchQueue.main.async and DispatchQueue.main.sync, and why can calling .sync from the main thread deadlock your app?
↑ 19 upvotes · 10 engineers asked this · Senior SDE
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Frequently asked questions
Explain how ARC (Automatic Reference Counting) works in Swift/Objective-C.
Explain how ARC (Automatic Reference Counting) works in Swift/Objective-C.
What is a retain cycle and how do you break one? Give an example using a delegate pattern and explain when to use weak vs unowned references.
Explain iOS memory management: ARC, strong/weak/unowned references, retain cycles. How does the system handle memory pressure? Walk through what happens when an app receives a memory warning and is then terminated.
Explain iOS memory management: ARC, strong/weak/unowned references, retain cycles. How does the system handle memory pressure? Walk through what happens when an app receives a memory warning and is then terminated.
Given a BST, find the closest value to a given target. Explain the O(log n) iterative approach using BST properties, and how the answer changes if the tree is unbalanced.
Given a BST, find the closest value to a given target. Explain the O(log n) iterative approach using BST properties, and how the answer changes if the tree is unbalanced.
How does Core Data work in iOS? Explain the managed object context, persistent store coordinator, and the fetch request pipeline. When would you use Core Data vs Realm vs SQLite directly?
How does Core Data work in iOS? Explain the managed object context, persistent store coordinator, and the fetch request pipeline. When would you use Core Data vs Realm vs SQLite directly?
In Swift, what is the difference between DispatchQueue.main.async and DispatchQueue.main.sync, and why can calling .sync from the main thread deadlock your app?
In Swift, what is the difference between DispatchQueue.main.async and DispatchQueue.main.sync, and why can calling .sync from the main thread deadlock your app?