Objective C Interview Questions and Answers for Freshers

Objective-C — the language that powers iOS and macOS development. Whether you’re a fresh-faced enthusiast or an aspiring developer, unlocking the secrets of Objective-C opens doors to creating powerful and intuitive applications. top interview questions and answers to ace your next tech interview.

Q1. What is Objective-C?

Ans: Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It is primarily used for macOS and iOS development.

Q2. What are the main features of Objective-C?

Ans:

1. Dynamic typing
2. Dynamic binding
3. Dynamic loading
4. Message passing
5. Categories and protocols
6. Automatic Reference Counting (ARC)

Q3. Explain the difference between #import and #include.

Ans: #import ensures that a file is included only once per compilation, preventing circular dependencies. #include allows a file to be included multiple times, which can lead to redundancy.

Q4. What are categories in Objective-C?

Ans: Categories allow you to add methods to existing classes without subclassing. This can be used to extend functionality or organize code better.

Q5. What are protocols in Objective-C?

Ans: Protocols define a list of methods that a class can implement. They are similar to interfaces in other languages and can be either optional or required.

Q6. How do you declare and use a property in Objective-C?

Ans: Properties are declared in the interface section using the @property keyword. For example:

objective

@interface MyClass : NSObject

@property (nonatomic, strong) NSString *name;

@end

The @synthesize directive is used in the implementation to generate getter and setter methods.

Q7. What is the purpose of @synthesize and @dynamic in Objective-C?

Ans:

1. @synthesize: Automatically generates getter and setter methods for a property.
2. @dynamic: Informs the compiler that getter and setter methods are implemented elsewhere.

Q8. Explain the concept of message passing in Objective-C.

Ans: Message passing in Objective-C is the process of sending a message to an object to call a method. This is done using square brackets, like [object message].

Q9. What is the difference between instancetype and id?

Ans: instancetype is used in method declarations to indicate that the method returns an instance of the class it is called on. id is a generic type for any Objective-C object.

Q10. What is Automatic Reference Counting (ARC)?

Ans: ARC is a memory management feature that automatically handles the retain and release of objects, reducing the need for manual memory management.

Q11. Explain the concept of delegation.

Ans: Delegation is a design pattern that allows one object to send messages to another object when an event occurs. It is commonly used for handling events and callbacks.

Q12. What is a nil pointer in Objective-C?

Ans: A nil pointer is a null pointer that can safely receive messages without causing a crash. It is used to represent an object that doesn’t exist.

Q13. How do you handle errors in Objective-C?

Ans: Errors in Objective-C are handled using the NSError class. Methods that can produce errors usually have an NSError pointer parameter to store error information.

Q14. What is the difference between shallow copy and deep copy?

Ans:

1. Shallow copy: Copies the reference to the object, not the object itself.
2. Deep copy: Creates a new instance of the object with the same values as the original.

Q15. How do you declare and use blocks in Objective-C?

Ans: Blocks are a way to define anonymous functions. They are declared using the ^ syntax:

objective

void (^myBlock)(void) = ^{

NSLog(@”Hello, World!”);

};

myBlock();

Q16. What is Key-Value Observing (KVO)?

Ans: KVO is a mechanism that allows objects to be notified of changes to specific properties of other objects. It is used to observe and respond to changes in state.

Q17. Explain the concept of Key-Value Coding (KVC).

Ans: KVC is a mechanism that allows accessing an object’s properties indirectly using strings. This can be used for dynamic property access and manipulation.

Q18. What are the different types of properties in Objective-C?

Ans:

1. nonatomic vs. atomic
2. strong vs. weak
3. copy
4. readonly vs. readwrite

Q19. How do you define a singleton class in Objective-C?

Ans: A singleton class is defined by creating a shared instance that is accessed globally:

objective

+ (instancetype)sharedInstance {

static MyClass *sharedInstance = nil;

static dispatch_once_t onceToken;

dispatch_once(&onceToken, ^{

sharedInstance = [[self alloc] init];

});

return sharedInstance;

}

Q20. What are the advantages of using Objective-C over other languages?

Ans:

1. Mature and stable language
2. Seamless integration with C and C++
3. Dynamic runtime and message passing
4. Extensive library support with Cocoa and Cocoa Touch

Summary

By familiarizing yourself with these common Objective-C interview questions and answers, you will be better prepared to demonstrate your knowledge and skills during your job interview. Read more: Online Interview Questions