Objective-C concepts interview questions — Easy
140 easy-level Objective-C concepts questions from our Objective-C bank, each with the correct answer and an explanation of why it is correct.
This topic slice is available to practise but is not yet part of our indexed set.
What this covers
Objective-C concepts appears throughout Objective-C interviews. At easy level, interviewers are typically checking that you know the fundamentals and can describe them precisely — definitions, defaults, and the basic mechanics. Work through these, then explain your answer out loud; the second part is what interviews actually test.
20 example questions
1. For a Objective-C codebase, what should you know about closures and capture — how surrounding state is captured by inner functions?
- A. It blocks the main thread until completion.
- B. Use the language's idiomatic closures and capture feature, which is designed for exactly this purpose.correct
- C. It is deprecated in current versions.
- D. It throws a runtime exception by default.
Why: Idiomatic Objective-C provides a built-in mechanism for closures and capture; relying on it (how surrounding state is captured by inner functions) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
2. For a Objective-C codebase, what should you know about type system — how types are checked and inferred?
- A. It requires an external framework.
- B. It is deprecated in current versions.
- C. It compiles to no-op.
- D. Use the language's idiomatic type system feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for type system; relying on it (how types are checked and inferred) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
3. A reviewer asks about immutability in your Objective-C code. What is the correct guidance regarding how immutable values are declared and enforced?
- A. Use the language's idiomatic immutability feature, which is designed for exactly this purpose.correct
- B. It is identical to the global variant.
- C. It is undefined behavior.
- D. It always returns null.
Why: Idiomatic Objective-C provides a built-in mechanism for immutability; relying on it (how immutable values are declared and enforced) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
4. A reviewer asks about pattern matching in your Objective-C code. What is the correct guidance regarding how values are destructured by shape?
- A. It is handled automatically by the garbage collector.
- B. Use the language's idiomatic pattern matching feature, which is designed for exactly this purpose.correct
- C. It is deprecated in current versions.
- D. It blocks the main thread until completion.
Why: Idiomatic Objective-C provides a built-in mechanism for pattern matching; relying on it (how values are destructured by shape) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
5. A reviewer asks about memory management in your Objective-C code. What is the correct guidance regarding how memory is allocated and reclaimed?
- A. It requires an external framework.
- B. Use the language's idiomatic memory management feature, which is designed for exactly this purpose.correct
- C. It blocks the main thread until completion.
- D. It is handled automatically by the garbage collector.
Why: Idiomatic Objective-C provides a built-in mechanism for memory management; relying on it (how memory is allocated and reclaimed) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
6. When working with data serialization in Objective-C, which statement best reflects how data is serialized to a portable format?
- A. It requires an external framework.
- B. It blocks the main thread until completion.
- C. Use the language's idiomatic data serialization feature, which is designed for exactly this purpose.correct
- D. It is undefined behavior.
Why: Idiomatic Objective-C provides a built-in mechanism for data serialization; relying on it (how data is serialized to a portable format) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
7. Which option correctly describes function definition in Objective-C, specifically how reusable functions are declared?
- A. It always returns null.
- B. It is identical to the global variant.
- C. Use the language's idiomatic function definition feature, which is designed for exactly this purpose.correct
- D. It allocates a new copy every time.
Why: Idiomatic Objective-C provides a built-in mechanism for function definition; relying on it (how reusable functions are declared) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
8. For a Objective-C codebase, what should you know about dependency management — how third-party libraries are added?
- A. It is undefined behavior.
- B. It is identical to the global variant.
- C. It requires an external framework.
- D. Use the language's idiomatic dependency management feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for dependency management; relying on it (how third-party libraries are added) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
9. In Objective-C, what is the idiomatic approach to variable scoping (how block vs function scope affects visibility)?
- A. It is deprecated in current versions.
- B. It is only available in unsafe mode.
- C. Use the language's idiomatic variable scoping feature, which is designed for exactly this purpose.correct
- D. It requires an external framework.
Why: Idiomatic Objective-C provides a built-in mechanism for variable scoping; relying on it (how block vs function scope affects visibility) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
10. Which option correctly describes concurrency model in Objective-C, specifically how concurrent or parallel work is expressed?
- A. It throws a runtime exception by default.
- B. It requires an external framework.
- C. Use the language's idiomatic concurrency model feature, which is designed for exactly this purpose.correct
- D. It is undefined behavior.
Why: Idiomatic Objective-C provides a built-in mechanism for concurrency model; relying on it (how concurrent or parallel work is expressed) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
11. When working with string handling in Objective-C, which statement best reflects how strings are represented and manipulated?
- A. It is undefined behavior.
- B. It always returns null.
- C. It blocks the main thread until completion.
- D. Use the language's idiomatic string handling feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for string handling; relying on it (how strings are represented and manipulated) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
12. In Objective-C, what is the idiomatic approach to null handling (how absence of a value is represented)?
- A. It allocates a new copy every time.
- B. It is handled automatically by the garbage collector.
- C. It always returns null.
- D. Use the language's idiomatic null handling feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for null handling; relying on it (how absence of a value is represented) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
13. For a Objective-C codebase, what should you know about module system — how code is organized into modules or packages?
- A. It is deprecated in current versions.
- B. It throws a runtime exception by default.
- C. It silently ignores the operation.
- D. Use the language's idiomatic module system feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for module system; relying on it (how code is organized into modules or packages) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
14. Which option correctly describes generics in Objective-C, specifically how code is parameterized over types?
- A. It always returns null.
- B. It blocks the main thread until completion.
- C. It throws a runtime exception by default.
- D. Use the language's idiomatic generics feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for generics; relying on it (how code is parameterized over types) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
15. In Objective-C, what is the idiomatic approach to asynchronous I/O (how non-blocking I/O is performed)?
- A. It is handled automatically by the garbage collector.
- B. It is undefined behavior.
- C. It compiles to no-op.
- D. Use the language's idiomatic asynchronous I/O feature, which is designed for exactly this purpose.correct
Why: Idiomatic Objective-C provides a built-in mechanism for asynchronous I/O; relying on it (how non-blocking I/O is performed) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
16. When working with equality semantics in Objective-C, which statement best reflects the difference between identity and value equality?
- A. Use the language's idiomatic equality semantics feature, which is designed for exactly this purpose.correct
- B. It is undefined behavior.
- C. It silently ignores the operation.
- D. It compiles to no-op.
Why: Idiomatic Objective-C provides a built-in mechanism for equality semantics; relying on it (the difference between identity and value equality) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
17. When working with error handling in Objective-C, which statement best reflects the recommended way to handle and propagate errors?
- A. It allocates a new copy every time.
- B. Use the language's idiomatic error handling feature, which is designed for exactly this purpose.correct
- C. It silently ignores the operation.
- D. It is identical to the global variant.
Why: Idiomatic Objective-C provides a built-in mechanism for error handling; relying on it (the recommended way to handle and propagate errors) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
18. A reviewer asks about performance tuning in your Objective-C code. What is the correct guidance regarding the most effective optimization strategy?
- A. Use the language's idiomatic performance tuning feature, which is designed for exactly this purpose.correct
- B. It always returns null.
- C. It is deprecated in current versions.
- D. It is identical to the global variant.
Why: Idiomatic Objective-C provides a built-in mechanism for performance tuning; relying on it (the most effective optimization strategy) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
19. Which option correctly describes testing approach in Objective-C, specifically the conventional unit-testing approach?
- A. It is only available in unsafe mode.
- B. Use the language's idiomatic testing approach feature, which is designed for exactly this purpose.correct
- C. It is deprecated in current versions.
- D. It always returns null.
Why: Idiomatic Objective-C provides a built-in mechanism for testing approach; relying on it (the conventional unit-testing approach) is clearer and safer than the alternatives, which misstate how Objective-C behaves.
20. In Objective-C, what is the idiomatic approach to collection iteration (the idiomatic way to iterate a collection)?
- A. It silently ignores the operation.
- B. It is handled automatically by the garbage collector.
- C. Use the language's idiomatic collection iteration feature, which is designed for exactly this purpose.correct
- D. It throws a runtime exception by default.
Why: Idiomatic Objective-C provides a built-in mechanism for collection iteration; relying on it (the idiomatic way to iterate a collection) is clearer and safer than the alternatives, which misstate how Objective-C behaves.