Interview questions in Mobile Dev, page 6
Explain backpressure in Kotlin Flows and its management operators
This tests your understanding of Flow's pull-based nature and performance tuning. A great answer defines suspension as the default backpressure, then details how buffer, conflate, and collectLatest optimize it.
Explain backpressure in Kotlin Flows and its management operators
This tests your understanding of Flow's sequential nature and strategies for decoupling producers and consumers. Explain default suspension, then detail buffer(), conflate(), and collectLatest(). A red flag is confusing conflate() with collectLatest().
Gesture Handler and Reanimated on the UI thread
Gesture Handler tracks gestures natively and Reanimated runs worklets on the UI thread, so animations driven by shared values continue smoothly even when the JS thread is blocked.
Which Instrument diagnoses scroll stuttering and dropped frames?
Tests whether you connect UI jank to Instruments data. A strong answer names the Core Animation or Time Profiler instrument, cites frame duration and hitch ratio, and correlates spikes with main-thread work.
Difference between Future<void> and void from an async function
Future<void> lets callers await and catch errors; void hides the Future, preventing await and leaving exceptions uncaught.
Describe coroutine cancellation mechanics and cooperative suspend functions
Tests cooperative cancellation mechanics. cancel() sets a Job to cancelling; suspend functions check this at suspension points and throw CancellationException, yet a tight non-suspending loop never checks and keeps running.
How does coroutine cancellation work internally?
Tests your grasp of cooperative cancellation. A good answer explains that cancel() sets a flag, suspend functions check it and throw CancellationException, and non-suspending loops need manual isActive checks.
How does coroutine cancellation work internally?
This tests your grasp of cooperative cancellation. Explain that cancel() sets a flag, causing a CancellationException at the next suspension point. A non-suspending loop must explicitly check isActive to stop.
navigate vs push in a Stack Navigator
Navigate goes to an existing instance of the route if present, otherwise pushes; push always adds a new instance onto the stack. Use push to revisit the same screen with new params.
How does Debug Memory Graph find leaks and retain cycles?
This tests knowledge of Xcode's heap visualization versus allocation sampling. A strong answer notes the graph shows objects, draws retain cycles as loops, and contrasts with Leaks time-based sampling. Red flag: expecting leak flags without inspection.
Describe the Dart event loop and queue execution order
Tests your grasp of Dart's single-threaded event loop priority. Great answers state: microtasks drain fully before the next event processes, cycling forever. Red flag: saying Future and scheduleMicrotask interleave in call order.
What is a reified type parameter in Kotlin?
Tests JVM type erasure and inline function mechanics. Strong answer: reified preserves generic types at runtime via inline expansion, enabling is T checks without Class<T> passing. Red flag: claiming reified works without inline or outside functions.
What is a reified type parameter in Kotlin?
Tests your grasp of JVM type erasure and Kotlin's solution. Explain that reified makes a generic type accessible at runtime inside an inline function, avoiding manual Class passing. A red flag is failing to link reified directly to inline functions.
Explain Kotlin's `reified` type parameters and their use case
Tests your grasp of JVM type erasure and Kotlin's solution. A great answer defines reified as making a generic type's Class accessible at runtime, explains this requires an inline function to substitute the type at the call site, and shows an example.
Stack Navigator vs Tab Navigator and nesting
A Stack pushes and pops screens for hierarchical drill-down; a Tab switches between parallel top-level sections. Nesting a Stack in each tab gives each tab its own independent push/pop history.
What build settings improve Time Profiler symbols in Release builds?
This tests debug symbol control in Xcode Release builds. Set DEBUG_INFORMATION_FORMAT to DWARF with dSYM, avoid stripping, citing larger size and slower links. Red flag: suggesting you disable optimizations, invalidating the performance profile.
Explain single-subscription vs broadcast Streams in Dart
Tests dart:async stream lifecycle. Outline: single-subscription allows one listener and emits on listen; broadcast supports many but drops events for late arrivals. Red flag: saying single-subscription allows multiple listeners or buffers events.
How would you implement a type-safe Kotlin DSL for a UI Form?
Tests Kotlin DSL scoping with lambda receivers and extensions. Strong answers sketch a Form builder using initTag, explain T.() -> Unit implicit this for child elements, and add DslMarker to block scope leaks. Red flag: describing it as simple method chaining.
Implement a type-safe DSL for a UI component in Kotlin
This tests your ability to design clean, hierarchical APIs using Kotlin's idiomatic features. A great answer defines model classes, then uses higher-order functions with lambdas with receiver to create a nested structure, and mentions @DslMarker for scope…
Implement a type-safe DSL in Kotlin for a UI component
Tests understanding of Kotlin's type-safe builders via lambdas with receivers. A great answer defines model classes, creates a top-level builder function taking a Receiver.() -> Unit lambda, and defines nested builder methods.
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