Objective-C Scenario-Based Questions 2025

This article concerns real-time and knowledgeable Objective-C Scenario-Based Questions 2025. It is drafted with the interview theme in mind to provide maximum support for your interview. Go through these Objective-C Scenario-Based Questions 2025 to the end, as all scenarios have their importance and learning potential.

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Disclaimer:
These solutions are based on my experience and best effort. Actual results may vary depending on your setup. Codes may need some tweaking.

1) Your iOS app’s memory spikes when scrolling a feed with images. In Objective-C, how would you reason about ARC, autorelease pools, and object lifetimes to fix it?

I’d assume ARC handles most retains/releases, but still check where large objects linger beyond their needed scope.
I’d wrap tight loops that create many autoreleased objects inside an @autoreleasepool block to drain sooner.
I’d confirm UIImage caching behavior and prefer downsampling or using imageNamed cautiously to avoid cache bloat.
I’d review strong vs weak references in view models and cells to prevent accidental long lifetimes.
I’d break large work into smaller chunks so memory can be reclaimed between iterations.
I’d profile with Instruments (Allocations/Leaks) to verify that peak memory drops after these changes.

2) A crash appears only under heavy load when dismissing a view controller. Where would you suspect retain cycles in Objective-C?

I’d first check blocks capturing self strongly in async tasks tied to the view controller.
I’d review delegates to ensure they’re marked weak/assign instead of strong to avoid cycles.
I’d check NSTimer, CADisplayLink, or notifications retaining the target without invalidation.
I’d confirm any NSOperation or GCD work releases references on completion.
I’d look at custom singletons or caches keeping strong arrays of controllers by mistake.
I’d reproduce under stress with Zombies enabled to pinpoint over-released or still-retained objects.

3) Product asks for faster startup. What Objective-C specific decisions help cut cold-start time safely?

I’d reduce +load and heavy work in +initialize to avoid runtime tax at launch.
I’d defer expensive singleton initialization until first use.
I’d move non-critical I/O off main thread and precompute lazily.
I’d shrink nib/storyboard graph or build lightweight initial UI first.
I’d trim dynamic swizzling or reflection at startup and do it on demand.
I’d measure improvements with signposts and time-to-interactive checks.

4) You see rare EXC_BAD_ACCESS after network retries. How would you reason about object ownership around callbacks?

I’d verify the callback queue and ensure UI-touching code runs on main safely.
I’d ensure completion blocks don’t capture stale pointers to model objects that got deallocated.
I’d promote to strong local references within short scopes when reading weak references.
I’d check that delegates are weak and the owner outlives the async operation.
I’d verify cancellation paths don’t free objects still referenced by in-flight blocks.
I’d use Zombies to catch messages to deallocated instances and fix the ownership chain.

5) Two teams disagree: categories vs class extensions for adding behavior. What’s your decision framework?

I use categories for logical, public behavior slices without new ivars.
I use class extensions for private methods or properties scoped to the implementation.
I avoid adding storage through associated objects unless I document lifetime and risk.
I keep category method names unique to prevent collisions and surprises.
I reserve swizzling for last-resort fixes and isolate it behind compile flags.
I prefer composition or protocols when behavior grows beyond a tidy slice.

6) A junior dev proposes heavy use of method swizzling to fix bugs. What risks and guardrails do you highlight?

Swizzling can break assumptions across updates and frameworks.
It’s hard to reason about call order and can create non-deterministic behavior.
I’d require targeted scope, clear comments, and runtime assertions.
I’d add automated tests around the swizzled paths.
I’d keep fallback toggles and metrics to detect regressions quickly.
I’d revisit the root cause first; swizzling stays a controlled workaround.

7) Your list screen stutters when formatting dates and layouts. How do you balance performance and readability?

I cache NSFormatter instances per thread instead of creating per cell.
I precompute heavy layout data off the main queue when possible.
I keep cell configuration minimal, pushing work into view models.
I reuse cells aggressively and reset state carefully.
I measure with Time Profiler and reveal hotspots before optimizing.
I document trade-offs so later changes don’t reintroduce cost.

8) You need concurrency but want predictable control. When do you prefer NSOperation over GCD?

I choose NSOperation for dependencies, cancellation, and priorities out of the box.
I prefer it when I need observable state (isFinished, isCancelled) and KVO hooks.
I use GCD for lightweight fire-and-forget or simple async hops.
I wrap GCD work in operations if I later need orchestration.
I ensure background work respects app lifecycle and memory pressure.
I confirm main-thread UI updates regardless of approach.

9) Your feature uses KVO for quick updates, but regressions keep popping up. How do you tame KVO in Objective-C?

I limit KVO to narrow, well-owned objects and documented keys.
I ensure balanced add/remove and prefer scoped observation helpers.
I avoid observing ephemeral objects that churn frequently.
I keep observers weak if the owner should not extend lifetime.
I add tests to catch keypath typos and removal paths.
I switch to delegation or notifications if KVO becomes fragile.

10) A module depends on runtime reflection to call hidden APIs. What’s your stance for long-term maintenance?

I avoid private APIs to keep store compliance and predictability.
I prefer explicit protocols and documented interfaces.
If reflection is used, I gate it behind capability checks and fallbacks.
I log usage to detect changes after OS updates.
I isolate the code and keep tests that simulate API absence.
I plan to refactor away once the official path exists.

11) You’re integrating an old Objective-C core with newer Swift modules. What pitfalls do you anticipate?

I define clear bridging headers and limit cross-language surface area.
I use NS_SWIFT_NAME and nullability to improve Swift ergonomics.
I ensure NSError patterns translate cleanly for Swift throws.
I standardize ownership with CF bridging where needed.
I keep ABI boundaries stable to avoid churn.
I add integration tests around bridging hot spots.

12) A model object keeps growing and now mixes networking, parsing, and caching. How do you de-couple it?

I pull protocol-driven boundaries: parsing, caching, transport as separate roles.
I move construction to factories and keep models as dumb data carriers.
I rely on composition instead of giant inheritance chains.
I document ownership: who holds strong refs and why.
I add thin facades so call sites don’t depend on internal modules.
I enforce this structure with unit tests to prevent regressions.

13) Your error handling feels noisy and inconsistent. How do you bring discipline with NSError patterns?

I define error domains per module and stable error codes.
I attach userInfo with recovery hints for better UX.
I prefer early returns and small scopes to keep code readable.
I convert underlying errors rather than dropping context.
I avoid exceptions for control flow, using them only for unrecoverables.
I track top error types and fix the root causes first.

14) A memory leak shows up around Core Foundation types. What’s your Objective-C plan without changing behavior?

I check toll-free bridged objects and ensure correct __bridge casts.
I balance CFRetain/CFRelease around ownership transfers.
I wrap CF types in small Objective-C objects to centralize lifetime.
I inspect Create/Copy rules to track who must release.
I unit test edge cases that missed release paths.
I confirm Instruments shows the leak gone after fixes.

15) Multiple modules want to listen for the same events. Delegate or notifications—how do you decide?

Delegate fits one-to-one relationships with clear ownership.
Notifications fit one-to-many broadcast without tight coupling.
I document payload format and thread expectations for notifications.
I keep delegates weak and narrowly scoped.
I avoid overusing notifications for request/response flows.
I add tests to ensure observers detach and don’t leak.

16) Your team adds “quick” associated objects to many categories. What’s your risk review?

Associated objects can mask hidden state and lifetimes.
I’d define keys centrally and document ownership expectations.
I’d keep usage minimal and prefer extensions with real properties when possible.
I’d avoid storing large graphs that complicate deallocation.
I’d add assertions for missing cleanup in dealloc paths.
I’d revisit design to push state into composed objects.

17) The app freezes during heavy JSON parsing. What Objective-C-centric improvements do you try first?

I move parsing to background queues with bounded concurrency.
I stream large payloads instead of loading all at once.
I predefine lightweight model builders to reduce intermediate objects.
I reuse buffers or formatters where safe.
I show progressive UI feedback to mask latency.
I measure with Time Profiler to confirm gains.

18) A feature relies on NSTimer but crashes after screen transitions. What patterns avoid this?

I prefer block-based timers with weak captures.
I invalidate timers in lifecycle dealloc or viewWillDisappear.
I consider CADisplayLink only if I truly need frame-level updates.
I centralize timers in a coordinator that outlives transient views.
I guard against retain cycles with weak/assign targets.
I test rapid present/dismiss cycles to ensure cleanup.

19) You must support older iOS versions with an Objective-C core. How do you plan API usage safely?

I gate features behind runtime checks and availability macros.
I provide no-op fallbacks where a capability is missing.
I keep compile-time flags for features that must be excluded.
I isolate version-specific code in small files.
I validate on oldest supported devices during CI.
I document minimum OS and expected behaviors clearly.

20) A colleague suggests replacing delegation with blocks everywhere. What’s your decision logic?

Blocks are great for one-off callbacks or simple chains.
Delegates shine for ongoing relationships and multiple events.
I weigh readability: too many blocks can nest and obscure flow.
I consider memory: blocks can capture strongly and leak.
I align on consistency at the module boundary.
I add lint rules to avoid accidental strong captures.

21) Your app uses many singletons and global state. What risks do you highlight and how do you reduce them?

Singletons create hidden coupling and testing pain.
I replace some with injected dependencies and protocols.
I keep necessary singletons focused with small APIs.
I clear or reset state between tests for isolation.
I document access rules and threading expectations.
I plan gradual refactors to contain global reach.

22) A UI list shows duplicate data after rapid refreshes. Where do you look first in Objective-C code?

I check diffing logic and ensure data source updates are atomic.
I confirm thread safety when mutating arrays and dictionaries.
I verify callbacks don’t deliver out-of-order responses.
I debounce refresh triggers to avoid overlapping reloads.
I reset reused cell state to avoid ghost values.
I log version stamps to ensure newest data wins.

23) Security review flags sensitive strings in memory. What language-level decisions help?

I reduce lifetime of sensitive objects and avoid long-term caching.
I zero buffers after use where applicable.
I prefer Keychain for storage rather than plist or NSUserDefaults.
I keep logs free of secrets and hash when necessary.
I clear pasteboard interactions promptly if used.
I design APIs that pass opaque tokens instead of raw secrets.

24) Your Obj-C framework will be used by multiple apps. How do you design the public API surface?

I keep headers minimal with clear nullability annotations.
I expose protocols and small value types where possible.
I document thread safety and ownership rules upfront.
I avoid exposing concrete classes that may change.
I version symbols and plan for deprecations.
I add samples and tests that mimic real integration.

25) The team debates MVC vs MVVM for a complex screen. What’s your objective take?

MVC is simple but can produce massive controllers in big screens.
MVVM helps push state and formatting out of controllers.
In Objective-C, I keep bindings explicit and testable.
I choose based on team skills and the feature’s complexity.
I prototype both quickly and measure cognitive load.
I standardize once we prove a pattern scales in our codebase.

26) A leak appears only when the app goes to background. Where would you investigate?

I’d inspect background tasks and completion handlers for retains.
I’d verify observers and timers pause or invalidate properly.
I’d check caches that grow during background fetch.
I’d review save operations that keep strong references.
I’d run Instruments with background transitions scripted.
I’d add logging to confirm who still holds references.

27) Build times are dragging. What Objective-C-specific steps help without harming quality?

I trim umbrella headers and reduce unnecessary imports via forward declarations.
I modularize large targets and enable parallel builds.
I avoid heavy macros and metaprogramming that slow parsing.
I cache codegen outputs where possible.
I watch out for giant Storyboards with slow IB compiles.
I measure with build logs to see the biggest wins.

28) A third-party SDK causes flaky crashes. How do you wrap it safely in Objective-C?

I isolate it behind a small facade with defensive checks.
I validate threading expectations at the boundary.
I sanitize and copy inputs to avoid lifetime issues.
I guard against nil or unexpected states with assertions.
I add runtime feature flags to disable risky paths.
I log SDK versions and add targeted health metrics.

29) Your analytics callbacks sometimes fire twice. Where do you hunt for the root cause?

I check that observers aren’t registered multiple times.
I confirm de-dup logic with idempotent event keys.
I ensure retries don’t re-emit success without checks.
I verify concurrent code doesn’t race to send.
I review lifecycle hooks to avoid double wiring.
I add tracing to follow a single event end-to-end.

30) The team wants to adopt nullability annotations across headers. How do you roll this out safely?

I start with external headers to improve integrator experience.
I annotate high-traffic APIs first and run static analysis.
I add NS_ASSUME_NONNULL_BEGIN blocks thoughtfully.
I fix places where nil is a real possibility.
I document expectations for parameters and returns.
I enforce new annotations in code review to keep drift low.

31) Your crash logs show selectors not recognized at runtime. How do you reason about these Objective-C issues?

I first suspect dynamic calls using performSelector: or missing method signatures.
I check categories to see if they were stripped out by the linker.
I confirm runtime registration for optional selectors in protocols.
I ensure typos or renames are caught by compiler warnings, not just at runtime.
I guard optional calls with respondsToSelector:.
I review weakly linked frameworks where symbols may not load.

32) A junior developer overuses macros for constants. How do you guide them toward safer Objective-C practices?

I explain macros don’t respect scope and lack type safety.
I encourage static NSString * const for string constants.
I prefer enums or NS_TYPED_ENUM for grouped values.
I highlight better debugging support when using constants.
I show how code completion and Swift bridging improve with proper constants.
I phase out macros gradually with code review enforcement.

33) Your team debates using ivars directly vs property access. How do you explain trade-offs?

Properties bring automatic memory management with ARC.
They also enable KVO and dynamic behaviors when needed.
Direct ivars are slightly faster but bypass encapsulation.
I recommend ivars only in init/dealloc where overhead is unnecessary.
Properties keep code consistent and future-proof.
I balance performance vs maintainability in high-frequency code.

34) An old codebase relies heavily on exceptions for flow. What’s your plan in Objective-C?

I remind that exceptions are for unrecoverable programmer errors.
I prefer NSError or return values for recoverable paths.
I review which exceptions can be downgraded to errors.
I wrap third-party code that may throw in try/catch safely.
I document the few legitimate exceptions left in the system.
I set a standard to prevent new misuse going forward.

35) A feature needs polymorphism. When do you prefer protocols over inheritance in Objective-C?

Protocols let me decouple behavior without forcing class hierarchies.
Inheritance is fine when objects share implementation, not just API.
Protocols bridge better to Swift with clean conformance.
They reduce diamond inheritance or fragile base class problems.
I combine protocols with categories for flexible behavior injection.
I measure complexity: small, well-defined contracts win over deep trees.

36) The project mixes manual retain/release with ARC. What pitfalls do you watch for?

Double releasing if legacy code calls release under ARC.
Leaks if autorelease pools aren’t respected correctly.
Bridging Core Foundation with mixed ownership rules.
Over-retaining due to compiler-inserted retains.
Confusion in crash logs showing mixed symbols.
I’d isolate legacy files with -fno-objc-arc and refactor gradually.

37) You must handle very large lists. What Objective-C collection patterns help performance?

I use NSCache for objects that can be regenerated.
I rely on lightweight placeholder objects for lazy loading.
I stream data instead of preloading entire arrays.
I choose NSDictionary lookups over linear searches.
I profile with Instruments to detect hot spots.
I document scaling assumptions for future maintainers.

38) Your QA team reports UI freezes when logging. What’s your Objective-C fix?

I switch synchronous file writes to async queues.
I batch log messages before flushing to disk.
I avoid NSLog in production, using lightweight logging instead.
I rotate logs to prevent giant files.
I redact sensitive info before storing.
I measure time spent in logging under stress tests.

39) The app frequently uses selectors stored as strings. How do you make this safer?

I prefer compiler-checked method references with @selector.
I wrap dynamic selectors in helper APIs.
I ensure respondsToSelector checks before invoking.
I document selector usage to avoid silent failures.
I reduce reliance on fragile string-based calls.
I adopt protocols or blocks where possible.

40) An Objective-C module is growing too monolithic. How do you modularize it effectively?

I split responsibilities into smaller targets or frameworks.
I define clear API boundaries using headers.
I add protocols so clients depend on abstractions, not implementations.
I enforce private headers vs public headers.
I test modules independently to catch regressions early.
I plan versioning for future reuse across apps.

41) You’re debugging race conditions with multiple threads. How do you approach synchronization?

I avoid unnecessary locks by redesigning ownership.
I use GCD serial queues instead of raw locks where possible.
I keep critical sections minimal to reduce contention.
I document invariants each thread can rely on.
I test with thread sanitizer to catch hidden races.
I profile under load to confirm stability.

42) Your manager asks: Why still use Objective-C when Swift exists? How do you justify?

Objective-C still powers many stable, large codebases.
Its runtime dynamism allows patterns Swift doesn’t.
Legacy apps require incremental migration, not rewrites.
It interoperates smoothly with Swift through bridging.
The ecosystem of libraries and tools is still mature.
It’s a practical business decision, not just a language choice.

43) A feature needs lightweight messaging across objects. What Objective-C tools fit?

NSNotificationCenter for broad decoupled communication.
Delegates for one-to-one structured callbacks.
Blocks for inline, lightweight callbacks.
KVO for property-level observation, cautiously.
Protocols for formal contracts between objects.
I choose based on scope, lifetime, and number of listeners.

44) The app must adapt to sudden low-memory warnings. How do you handle it?

I register for UIApplicationDidReceiveMemoryWarning.
I clear in-memory caches proactively.
I drop non-critical images or data and reload later if needed.
I save critical state to disk so recovery is safe.
I prefer NSCache since it auto-purges under pressure.
I monitor memory in Instruments to validate response.

45) The team wants faster unit tests. What Objective-C-specific improvements do you apply?

I mock dependencies with OCMock or hand-rolled stubs.
I reduce reliance on global singletons in tests.
I parallelize tests where isolation allows.
I avoid hitting the main runloop unnecessarily.
I separate pure logic tests from heavy UI tests.
I track flaky tests and fix underlying race issues.

46) A sudden crash shows `unrecognized selector sent to instance`. How do you systematically debug?

I reproduce with Zombies to catch deallocation issues.
I confirm object class matches what I expect.
I check swizzling or categories for overwritten selectors.
I trace call site lifetimes to ensure valid instances.
I add runtime logs to confirm selector availability.
I write tests around the failing path after fixing.

47) An API requires secure serialization. How do you design it in Objective-C?

I prefer NSSecureCoding over plain NSCoding.
I validate class types before decoding.
I whitelist expected classes during unarchiving.
I encrypt serialized blobs before persisting.
I sign data for integrity if transmitting externally.
I audit deserialization paths for injection risks.

48) You’re asked to reduce binary size. What Objective-C techniques help?

I strip unused architectures with build settings.
I remove dead categories or swizzles.
I audit large assets like nibs and images.
I prefer lightweight model objects over bloated ones.
I consolidate duplicate code into shared helpers.
I enable bitcode or linker optimizations when allowed.

49) The app shows subtle memory leaks only after long use. What habits help detect them early?

I run Instruments regularly during development.
I write lightweight stress tests to mimic long sessions.
I monitor NSCache and collections for growth trends.
I add weak self patterns in blocks consistently.
I review timers and notifications for cleanup.
I track memory snapshots over time in CI.

50) A customer complains about sluggish search results. How would you optimize in Objective-C?

I debounce input to avoid overloading queries.
I index data into dictionaries or sets for faster lookup.
I paginate results instead of loading everything.
I push heavy work onto background queues.
I cache popular queries for reuse.
I measure time complexity and fix hotspots first.

51) Your old Obj-C code has no nullability annotations. What risks do you explain?

Callers may misuse APIs expecting non-nil values.
Swift clients get unclear optionals without annotations.
It reduces compiler static analysis effectiveness.
It leads to runtime crashes for simple mistakes.
Migration to Swift gets harder without contracts.
Annotations bring safer, clearer intent for all devs.

52) How do you prevent Objective-C categories from creating hidden conflicts?

I prefix category methods with module-specific identifiers.
I avoid redefining common selector names like init.
I document category usage in headers.
I group categories logically, not randomly.
I unit test to detect collisions early.
I switch to composition if conflicts keep growing.

53) Your analytics team asks for real-time event tracking. How do you balance it in Objective-C?

I batch events to avoid hammering the network.
I flush at key lifecycle points like backgrounding.
I ensure thread safety in event queue management.
I strip PII before transmitting to stay compliant.
I monitor performance overhead of tracking.
I provide a fallback if servers are unavailable.

54) The business asks: why avoid retain cycles so strongly? How do you explain simply?

Retain cycles mean objects never get deallocated.
That grows memory use until the app crashes.
It’s invisible to users until performance suffers.
Weak references break cycles safely.
Cleaning up cycles improves app stability.
It’s cheaper to prevent than to debug later.

55) A crash log shows CFRelease on already freed memory. How do you handle?

I review bridging casts and ownership transfers.
I confirm correct balance of CFRetain/CFRelease.
I use __bridge_transfer where ARC should take ownership.
I isolate legacy CF code into safer wrappers.
I run static analysis for leaks or over-releases.
I test stress paths to confirm stability.

56) How do you manage risk when mixing Obj-C categories with swizzling in production?

I minimize swizzling to critical bugs only.
I log when swizzled methods execute for traceability.
I isolate swizzles in one file with documentation.
I add tests for both original and swizzled behavior.
I keep feature flags to disable if needed.
I revisit regularly to remove once no longer necessary.

57) A colleague asks: why not use ARC everywhere? What limitations exist?

ARC can’t manage Core Foundation without explicit bridging.
It doesn’t handle custom memory pools.
It sometimes adds overhead with hidden retains/releases.
It makes debugging harder if you assume manual control.
Certain performance-tuned code prefers manual retain/release.
But overall, ARC is safer for most of the codebase.

58) Your app’s startup time worsens after adding categories. How do you analyze?

I check +load methods in categories firing at launch.
I delay heavy swizzling or setup until first use.
I profile startup with Instruments’ launch template.
I consolidate duplicate logic across categories.
I ensure no unnecessary logging at launch.
I optimize nib/storyboard loading paths too.

59) You’re asked to train juniors on Obj-C. What core lessons do you emphasize?

Memory management basics with ARC and weak/strong.
Delegation, protocols, and categories as building blocks.
Error handling via NSError, not exceptions.
Runtime dynamism with selectors and messaging.
Best practices: avoid retain cycles, swizzling as last resort.
Clean coding with modular design and tests.

60) A senior manager asks: what’s the business benefit of maintaining Objective-C expertise today?

It keeps decades of stable, revenue-generating apps alive.
It reduces migration risk by keeping skilled support.
It allows gradual Swift adoption instead of costly rewrites.
It ensures faster debugging of legacy issues.
It helps onboard new features without breaking old code.
It safeguards institutional knowledge in the org.

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