Swift Language and Memory Management Questions
Deep understanding of Swift syntax, type system, ARC (Automatic Reference Counting), weak/strong references, and avoiding retain cycles. Understanding of value types vs reference types and when to use each. Familiarity with modern Swift features like async/await, property wrappers, and generics.
HardSystem Design
48 practiced
You need to implement a high-throughput Swift data pipeline that processes millions of small messages per second. Describe type and memory allocation strategies to minimize ARC overhead and heap churn: use of value types vs reference types, object pools, arenas, preallocated buffers, and other tactics to reduce allocations and retain/release cost.
MediumTechnical
38 practiced
Given the following Swift code snippet, identify any retain cycles and fix them. Code: class ViewController { var completion: (() -> Void)? func viewDidLoad() { network.fetch { self.handleResponse() } } func handleResponse() { completion = { self.dismiss() } } } Explain each retain cycle and propose a memory-safe solution.
HardTechnical
33 practiced
Discuss how isKnownUniquelyReferenced helps implement copy-on-write semantics by testing whether a class instance backing a struct is uniquely referenced. Explain potential race conditions if used unsafely in multithreaded contexts and how to mitigate them (locks, actor isolation, atomic operations).
HardTechnical
36 practiced
Design a safe Swift wrapper API for a C library that returns CoreFoundation-style opaque objects requiring manual CFRetain/CFRelease. Show how you would use Unmanaged<T> in the wrapper, demonstrate safe ownership transfer, and explain thread-safety and lifetime guarantees for Swift clients.
HardTechnical
44 practiced
Write a small, leak-free KVO wrapper in Swift that observes an Objective-C property and invokes a closure when the value changes. Ensure observers are removed and that the wrapper does not create retain cycles between observer and observed object. Show how to use it safely from a Swift class.
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