Advanced interview questions in iOS & Swift, page 2
Diagnose dropped frames during animation
Use Core Animation and color-debug options to spot off-screen passes, blending, and overdraw; cache, flatten, and set shadowPath.
Build an interruptible custom VC transition
A delegate vends an animator (UIViewControllerAnimatedTransitioning) for the visuals and an interactive controller (UIViewControllerInteractiveTransitioning) driven by a pan to scrub progress and…
Animate a SwiftUI Shape morphing point count
Expose a continuous sides value as animatableData so SwiftUI interpolates it, then compute the path from that fractional value each frame.
Apply a CIFilter to a live camera feed
Use AVCaptureSession with AVCaptureVideoDataOutput, receive CMSampleBuffers in captureOutput via the sample buffer delegate on a serial queue, filter with CIImage, drop late frames.
React to location authorization changed in Settings
Implement locationManagerDidChangeAuthorization, which fires on launch and whenever status changes, read authorizationStatus, and start updates when authorized.
Recognize objects in ARKit with a Core ML model
Pull the frame's capturedImage, run Vision/Core ML off the main thread, raycast the 2D detection point into the scene, add an ARAnchor.
Diagnosing and stabilizing flaky XCUITests
Identify timing races, animations, network variance, and shared state; fix with expectations, controlled launch state, and isolation.
Driving app state via launch arguments in XCUITest
Pass launchArguments and launchEnvironment, read them at startup to seed auth and flags, bypassing slow UI steps.
Developing a local Swift Package alongside an app
Add the package as a local dependency by dragging its folder into the project or workspace, so Xcode references the source on disk and rebuilds edits immediately.
App Thinning: slicing, bitcode, and on-demand resources
Slicing delivers only the assets and code a device needs; bitcode let Apple recompile and re-optimize; on-demand resources defer large assets until requested.
Securely managing signing assets in CI/CD
Keep encrypted certificates and profiles in a controlled store or fastlane match repo, inject the decryption key and credentials via CI secrets, install into a temporary keychain per run.
Privacy manifests and the app privacy report
PrivacyInfo.xcprivacy declares collected data types, tracking, and reasons for required-reason APIs; Xcode aggregates your manifest plus SDK manifests into a privacy report.
The dynamic keyword and message dispatch
Dynamic forces Objective-C message dispatch via objc_msgSend, enabling KVO and swizzling, at the cost of skipping inlining and devirtualization.
Verifying and avoiding copy-on-write overhead
Confirm extra copies via isKnownUniquelyReferenced or instruments and the retain trace; ensure unique references, mutate inout/in place, reserveCapacity, avoid aliasing.
Debugging a closure capture leak in a third-party library
Use the Memory Graph Debugger to inspect retain paths, the Leaks and Allocations instruments, and malloc stack logging; trace the cycle before patching.
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