Frequently Asked iOS Developer Interview Questions and Answers

iOS developers are responsible for developing applications for Apple's mobile operating system. According to Apple over 30 million registered iOS Developers exist. This means that the competition is high. 

If you are looking for a job to work as an iOS Developer, it is likely that you will face technical iOS Developer interview questions.

As a result, you need to correctly answer iOS Developer interview questions to catch the attention of the hiring manager. We know that interviews can be stressful for everyone. In this article, we will thoroughly discuss iOS developer interview questions and answers. 👇💡

 

1. What is iOS?

iOS is a mobile operating system developed by Apple Inc. It is used on Apple devices such as iPhone, iPad, and iPod Touch.

 

2. What is Swift?

Swift is a general-purpose, open-source programming language used for developing iPadOS, macOS, tvOS, watchOS, and iOS applications. It was developed by Apple in 2014. 

The purpose of Swift is to develop iOS applications. According to Swift.org, Swift is a safe and fast programming language. Swift also has a growing community. The Swift source code is available on GitHub, which makes it easy for everyone to access the code.

 

3. What are the differences between Android and iOS?

🆚 Android - A mobile operating system offered by Google for Android devices. It is found on smartphones and tablets. Various programming languages, including C, Java, and C++, have been used in its development.

🆚 iOS - An operating system offered by Apple for Apple devices. It is the second most popular mobile operating system worldwide after Android. It is used on Apple mobile devices such as iPhone, iPod Touch, etc. Development has utilized Objective-C, Swift, and C++.

 

4. What is the difference between Swift and Objective-C?

🆚 Swift is a programming language released by Apple in 2014. 

🆚 Objective-C is an older programming language developed by Apple. 

🆚 Swift is easier, more readable, and faster compared to Objective-C.

 

5. What is a category in Objective-C?

Categories in Objective-C are tools that allow adding functionality to an object without having to modify the object itself or use subclassing. 

 

6. What steps do you follow when developing an application?

1. Determining requirements
2. Creating design
3. Coding
4. Testing
5. Publishing

 

7. What is CocoaPods?

CocoaPods is a package manager used for managing dependencies in Swift and Objective-C programming languages. Developers use CocoaPods to create simple and easy code. 

With the help of CocoaPods, developers use code that has already been created and prepared by other developers instead of coding everything from scratch. Cocoapods also serve as a central repository for sharing your code with others. 

 

8. What are Cocoa and Cocoa Touch?

Cocoa Touch is a user interface framework provided by Apple for creating software applications for products like iPhone, iPad, and iPod Touch. It is designed to work with Swift, Cocoa, and Cocoa Touch frameworks and Objective C codes written for Apple products.

 

10. What is Core Data?

Core Data is a framework developed and maintained by Apple. Core Data is the MVC's M, which is the model layer of applications. 

 

11. What do you need to do to use Core Data in your application?

Core Data is a framework used for storing data in iOS applications. To use Core Data in an application, follow these steps:

1️⃣ Create the Core Data model.

2️⃣ Save the data appropriately according to the model.

3️⃣ Use fetch operations to display the data.

 

12. What is ARC and how does it work?

Automatic Reference Counting (ARC) is a feature of the Objective-C compiler and Swift’s memory tracking system. It was developed by Apple to simplify memory management and prevent memory leaks. 

ARC eliminates the need for developers to perform manual memory management. It decides whether objects should remain in memory or be deleted from memory on its own. This minimizes improper memory usage.

ARC automatically manages the memory of objects used in the program. When an object is created in the program, ARC generates a reference count for that object. This count determines how many references the object has. If a new reference is created to an object, the count increases. If a reference is removed, the count decreases. If an object's reference count drops to zero, ARC automatically deletes the object from memory.

 

13. What is a Delegate and what is it used for?

A delegate is when an object delegates a task it wants to perform (delegator) to another object, which takes over and performs the task (delegate). This delegation between objects is called a delegate.

Many classes in the iOS SDK provide one or more delegation points. This allows one object to notify another object when an event occurs. Delegation makes the code more modular and reduces code repetition.

 

14. What steps are followed to set a delegate in Swift?

1️⃣ Define the protocol.

2️⃣ Create an instance of the delegate.

3️⃣ Call the delegate.

4️⃣ Implement the delegate.

5️⃣ Assign the delegate.

 

15. What is 'required init' in Swift?
Init is the process of preparing an instance of a class, struct, or enumeration. In Swift, the "required init" keyword is used to enforce that a class must be initialized in a specific way by its subclasses.

The required keyword signifies that subclasses must implement this method before overriding a method defined by the superclass.

 

16. What is the syntax for init() in Swift?

The class’s initializer method is defined by placing parentheses next to the “init” keyword. 

 

17. What is 'mutating' in Swift?

"Mutating" is a keyword used to indicate that a method modifies the properties of a value type. In Swift, the "mutating" keyword is used to indicate that a function can change the structure of a value type. 

 

18. What are the common design patterns recommended for iOS applications?

Among the design patterns recommended by Apple for iOS applications are Delegate, MVC, Observer and Singleton are included.

 

19. What is the UIKit framework?

The UIKit framework provides the essential objects needed when creating applications for iOS and tvOS. These objects are used to display content on the screen, interact with that content, and manage interactions with the system. 

 

20. What is the UIKit View Controller lifecycle?

The UIKit View Controller lifecycle consists of the stages a View Controller goes through from the moment it is created until it loses its functionality. 

The UIKit View Controller lifecycle is generally divided into two main phases: loading and displaying the view lifecycle. This lifecycle continuously occurs while the View Controller is visible on the screen.

 

21. What is the difference between static typing and dynamic typing?

Static typing and dynamic typing are important concepts. 

👉 Static typing means that all code is checked before the program runs. Swift uses static typing. 

👉 Dynamic typing means that code is executed and its result is displayed while the program is running. Objective-C uses dynamic typing. 

 

22. What is type inference?

Type inference is a feature that allows the compiler to automatically determine the data type of a variable. This helps make the code more readable and concise. It also allows the code to be written more quickly. 

 

23. Can objects in Objective-C and Swift be nil?

Objective-C and Swift allow objects to be nil.

 

24. What is a protocol?

A protocol is an interface that includes abstract methods, constants, and variables. Protocols provide functionality between classes. Multiple protocols can be adopted. 

 

25. Which JSON framework is supported by iOS?

SBJson framework is supported by iOS. It is a JSON parser and generator for Objective-C. SBJson provides flexible APIs and additional control that make using JSON easier.

 

26. What does GCD (Grand Central Dispatch) mean in iOS?

Grand Central Dispatch (GCD) is an API that allows users to manage threads in the background to run concurrent tasks. Grand Central Dispatch enables running multiple background tasks simultaneously in the background without affecting the main thread. 

 

27. What are the ways to achieve concurrency in iOS?

1. Threads
2. Dispatch queues
3. Operation queues

 

28. When would you say that iOS applications are not running?

An application can be said to be not running when it is not launched or when it is terminated by the system during runtime. 

 

29. What is iBeacon?

🗺 iBeacon is a small-scale network device that uses Bluetooth Low Energy (BLE) and acts as a transmitter to detect and track smartphones. The Apple iBeacon protocol is used to provide location-based notifications/services by allowing wireless devices to connect without human intervention using BLE.

 

30. What is Operator Overloading?

Operator functions (Operator Overloading) allow you to change the behavior of existing operators and add new operators.

+, * and / symbols are known as operators.

 

31. What is TVMLKit?

TVMLKit acts as a bridge between TVML, JavaScript , and tvOS software. The TVMLKit framework allows TVMLKit JS and TVML files to be rendered from within the tvOS application.

 

32. What is NSError in Swift?

In Swift, NSError is a class primarily used to define errors and exceptional situations. It is typically inherited from the Objective-C era and can be used when interacting with Objective-C code. An NSError object is used to represent situations where a function or method call has failed.