55 Must-Know Objective-C Interview Questions and Answers 2024

Objective-C Fundamentals

1.
Describe the basic structure of an Objective-C class.
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2.
How do you define and implement a method in Objective-C?
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3.
What are the built-in data types available in Objective-C?
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4.
How do you work with NSString, and how is it different from a C-style string?
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5.
Explain the difference between a class method and an instance method.
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6.
Describe the use of pointers in Objective-C.
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7.
What is a property in Objective-C, and how do you use the @synthesize directive?
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8.
How do you declare and use a block in Objective-C?
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9.
Provide examples of various control flow structures available in Objective-C.
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10.
How do you create and use an enum in Objective-C?
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Object-Oriented Features

11.
How does inheritance work in Objective-C?
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12.
What is polymorphism, and how is it achieved in Objective-C?
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13.
Explain the concept of encapsulation and give an example in the context of Objective-C.
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14.
How do you define a class in Objective-C, and what is the significance of the NSObject class?
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15.
What is method overloading, and is it supported in Objective-C?
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16.
How is message passing implemented in Objective-C?
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17.
Explain the use of the id type and when it is useful.
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Memory Management

18.
Describe the process of manual reference counting in Objective-C.
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19.
Explain what automatic reference counting (ARC) is and how it works.
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20.
Compare and contrast ARC with garbage collection.
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21.
How do you manage memory in Objective-C when dealing with Core Foundation objects?
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22.
What are weak and strong references in Objective-C?
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23.
Demonstrate how to use the retain, release, and autorelease methods in MRC.
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Objective-C Collections

24.
What are the differences between NSArray and NSMutableArray?
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25.
How do you work with dictionaries in Objective-C?
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26.
Explain the benefits of using NSSet over NSArray.
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Protocols and Delegates

27.
What is a protocol in Objective-C, and how do you define one?
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28.
How do you conform a class to a protocol in Objective-C?
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29.
Provide an example of how delegates are used in Objective-C.
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30.
What is the difference between formal and informal protocols?
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31.
Explain the purpose of the @optional and @required keywords in protocols.
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Categories and Extensions

32.
What are categories in Objective-C, and how do you create one?
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33.
Explain how extensions (class continuations) differ from categories.
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34.
Can you add instance variables in categories or extensions?
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Error Handling and Exceptions

35.
How do you handle exceptions in Objective-C?
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36.
Demonstrate how to use @try, @catch, and @finally blocks.
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37.
What best practices would you recommend for error handling in Objective-C?
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Interoperability with Swift and C

38.
How do you call Objective-C code from Swift and vice versa?
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39.
Discuss the key considerations when using Objective-C and C together.
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40.
How do you manage bridging headers in a mixed Objective-C and Swift project?
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Objective-C Runtime

41.
Explain what the Objective-C runtime is and why it’s important.
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42.
Describe method swizzling and provide a use case for it.
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43.
How does Objective-C support dynamic typing and dynamic method resolution?
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Advanced Features

44.
What are blocks in Objective-C, and how do you use them?
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45.
How do you work with threads in Objective-C?
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46.
Describe GCD and how it’s used in Objective-C for concurrency.
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47.
Explain the concept of key-value coding (KVC) and key-value observing (KVO).
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48.
How do you implement synchronization in Objective-C to handle concurrent access to objects?
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Best Practices in Objective-C Development

49.
How do you ensure code quality and maintainability in an Objective-C project?
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50.
What are some common performance optimization techniques in Objective-C?
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51.
Discuss the importance of naming conventions and code organization in Objective-C.
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Objective-C and Cocoa Frameworks

52.
How does the Cocoa framework utilize Objective-C features?
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53.
Describe the delegation pattern as used in Cocoa and Cocoa Touch.
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54.
What is the responder chain in Cocoa, and how does it work?
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55.
Discuss the use of Core Data in Objective-C for data persistence.
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55 Objective-C interview questions

Describe the basic structure of an Objective-C class.

How do you define and implement a method in Objective-C?

What are the built-in data types available in Objective-C?

How do you work with NSString, and how is it different from a C-style string?

Explain the difference between a class method and an instance method.

Describe the use of pointers in Objective-C.

What is a property in Objective-C, and how do you use the @synthesize directive?

How do you declare and use a block in Objective-C?

Provide examples of various control flow structures available in Objective-C.

How do you create and use an enum in Objective-C?

How does inheritance work in Objective-C?

What is polymorphism, and how is it achieved in Objective-C?

Explain the concept of encapsulation and give an example in the context of Objective-C.

How do you define a class in Objective-C, and what is the significance of the NSObject class?

What is method overloading, and is it supported in Objective-C?

How is message passing implemented in Objective-C?

Explain the use of the id type and when it is useful.

Describe the process of manual reference counting in Objective-C.

Explain what automatic reference counting (ARC) is and how it works.

Compare and contrast ARC with garbage collection.

How do you manage memory in Objective-C when dealing with Core Foundation objects?

What are weak and strong references in Objective-C?

Demonstrate how to use the retain, release, and autorelease methods in MRC.

What are the differences between NSArray and NSMutableArray?

How do you work with dictionaries in Objective-C?

Explain the benefits of using NSSet over NSArray.

What is a protocol in Objective-C, and how do you define one?

How do you conform a class to a protocol in Objective-C?

Provide an example of how delegates are used in Objective-C.

What is the difference between formal and informal protocols?

Explain the purpose of the @optional and @required keywords in protocols.

What are categories in Objective-C, and how do you create one?

Explain how extensions (class continuations) differ from categories.

Can you add instance variables in categories or extensions?

How do you handle exceptions in Objective-C?

Demonstrate how to use @try, @catch, and @finally blocks.

What best practices would you recommend for error handling in Objective-C?

How do you call Objective-C code from Swift and vice versa?

Discuss the key considerations when using Objective-C and C together.

How do you manage bridging headers in a mixed Objective-C and Swift project?

Explain what the Objective-C runtime is and why it’s important.

Describe method swizzling and provide a use case for it.

How does Objective-C support dynamic typing and dynamic method resolution?

What are blocks in Objective-C, and how do you use them?

How do you work with threads in Objective-C?

Describe GCD and how it’s used in Objective-C for concurrency.

Explain the concept of key-value coding (KVC) and key-value observing (KVO).

How do you implement synchronization in Objective-C to handle concurrent access to objects?

How do you ensure code quality and maintainability in an Objective-C project?

What are some common performance optimization techniques in Objective-C?

Discuss the importance of naming conventions and code organization in Objective-C.

How does the Cocoa framework utilize Objective-C features?

Describe the delegation pattern as used in Cocoa and Cocoa Touch.

What is the responder chain in Cocoa, and how does it work?

Discuss the use of Core Data in Objective-C for data persistence.

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What is a property in Objective-C, and how do you use the `@synthesize` directive?

Explain the use of the `id` type and when it is useful.

Demonstrate how to use the `retain`, `release`, and `autorelease` methods in MRC.

Explain the purpose of the `@optional` and `@required` keywords in protocols.

Demonstrate how to use `@try`, `@catch`, and `@finally` blocks.