Interview questions in Mobile Dev, page 2
What problem does late solve in Dart?
Tests definite assignment and lazy init in null-safe Dart. Strong answers cover: deferred non-nullable field init, lazy final evaluation, and LateInitializationError on early access. Red flag: treating late as nullable or saying it bypasses null safety.
What are the primary advantages of using a data class?
Tests Kotlin boilerplate reduction and value semantics. Name three generated functions like equals, hashCode, and copy; explain structural equality; and show copy updating immutable UI state.
What are the advantages of a Kotlin data class?
Tests knowledge of Kotlin's boilerplate reduction for data holders. A good answer defines the advantage (conciseness), names generated functions like equals, hashCode, and copy, and explains copy for immutable state updates.
What are the advantages of a Kotlin data class and its functions?
Tests knowledge of Kotlin's idiomatic features. A good answer explains the main advantage (boilerplate reduction), lists generated functions like toString() and equals(), and describes copy() for immutable state updates.
Inline styles vs StyleSheet.create
Styles are JS objects passed to the style prop; StyleSheet.create registers styles once for stable references and validation, while inline objects recreate on each render.
Why can't you subscript a Swift String with an Int?
Characters are extended grapheme clusters of variable byte width, so integer offsets are not O(1) or meaningful; String.Index is an opaque position you advance via the collection.
How do you use collection-if and collection-for to declaratively build a list?
Tests Dart's declarative collection control-flow features. Answer: show collection-for to filter inside a literal, collection-if for conditional items, and combine both in one expression. Red flag: imperative loops and add() instead of literal syntax.
Explain lateinit var versus val by lazy in Android
Tests deferred initialization and lifecycle coupling. Great answers contrast lateinit var's imperative assignment with lazy's first-access delegation, mapping lateinit to injected Activity fields and lazy to expensive computed objects.
lateinit var vs. val by lazy in Android
Tests your grasp of Kotlin's non-nullable property initialization. Define lateinit (mutable, framework-init) vs. lazy (immutable, deferred-init). Use lateinit for Views in onCreate and lazy for expensive objects. Red flag: confusing their mutability.
lateinit var vs. val by lazy in Android
Tests your grasp of Kotlin property initialization and its lifecycle implications. A good answer contrasts mutability (var/val), initialization timing, and thread safety.
View vs Text and nesting rules
View is a flexbox layout container; Text renders and lays out text with inheritance. Text nests inside Text and inherits style; View inside Text is constrained and discouraged.
What is @autoclosure and when is it useful?
@autoclosure wraps an argument expression in a closure so it evaluates lazily only if used, enabling clean APIs like assert and the ?? operator.
What is a Dart closure? Write a function that returns a function.
Tests lexical scoping: define a closure as a function plus its captured environment, show a makeAdder where the inner function uses a parent variable after the parent returns.
Explain higher-order functions and implement filterAndTransform
Tests whether you can define higher-order functions and use lambdas idiomatically in Kotlin. A strong answer defines HOFs as functions that take or return functions, then implements filterAndTransform with filter and map.
Explain and implement a higher-order function in Kotlin
Tests your grasp of functions as first-class citizens. Define a higher-order function, explain it takes/returns functions, then implement filterAndTransform using the specified lambdas.
Explain and implement a Kotlin higher-order function
Tests understanding of first-class functions and lambda usage. First, define a higher-order function (HOF) as one that takes/returns functions. Then, implement the requested function, iterating to apply the predicate and transform.
Default flexDirection and header-content-footer layout
Default flexDirection is column, unlike web's row; give the root flex 1, fixed heights to header and footer, and flex 1 to a scrollable middle.
Swift struct vs class: differences and when to choose each
Tests value vs reference semantics and let mutability. Strong answers contrast copy behavior with shared references, note allocation tendencies, and choose struct for value semantics or class for identity.
What are Dart extension methods? Implement toIntOrDefault on String.
Tests Dart extension syntax and static resolution. A strong answer defines an extension on String, uses int.tryParse with a fallback, and notes extensions do not mutate the original type. Red flag: using try-catch over tryParse or claiming dynamic dispatch.
When would you use a sealed class instead of an enum?
This tests closed hierarchies versus singleton constants. A strong answer contrasts enums with sealed class instances, shows a NetworkResult example with data-bearing branches, and highlights exhaustiveness.
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