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Table of contents
1.
Introduction
2.
What is iOS?
3.
Features of the iOS Platform
4.
iOS Interview Questions for Freshers
4.1.
1. Explain what TVMLKit is.
4.2.
2.  Define Bundle ID?
4.3.
3. Which framework is used to construct the application’s user interface?
4.4.
4. Explain what Code Coverage is?
4.5.
5. How can you open the Code Snippet Library in Xcode?
4.6.
6. When is the category used?
4.7.
7. Explain what the Responder Chain is?
4.8.
8. When is an app said to be not running the state?
4.9.
9. Explain the object?
4.10.
10. When would you say that an app is in an active state?
5.
iOS Interview Questions for Intermediate
5.1.
11. Name some important data types found in objective-C?
5.2.
12. What is iBeacon?
5.3.
13. What is Method Swizzling?
5.4.
14.  What are the methods to achieve concurrency?
5.5.
15. Which method can we use to perform final utilization before displaying the app to the user?
5.6.
16. What does KVO stand for?
5.7.
17. What is GCD?
5.8.
18. What are the two different smart groups in Xcode?
5.9.
19. What are the programming languages used for iOS development?
5.10.
20.  What is ARC?
6.
iOS Interview Questions for Experienced
6.1.
21. Which JSON framework does iOS support?
6.2.
22. What is the difference between KVC and KVO?
6.3.
23. Explain the Observer Pattern?
6.4.
24. Explain the Adapter Pattern?
6.5.
25. What is Operator Overloading?
6.6.
26. What is the difference between atomic and nonatomic synthesized properties?
6.7.
27. Define Cocoa/Cocoa touch?
6.8.
28. What is the difference between Viewdidload and Viewdidappear? 
6.9.
29. What methods can we follow to achieve concurrency in iOS?
6.10.
30. Explain layer objects in Swift.
7.
iOS MCQ
7.1.
1. Which programming language is primarily used for iOS development?
7.2.
2. What is the name of Apple's integrated development environment (IDE) for iOS app development?
7.3.
3. What is the purpose of the @IBOutlet keyword in iOS development?
7.4.
4. Which design pattern is most commonly used in iOS development?
7.5.
5. What is SwiftUI?
7.6.
6. What is the default file format for storyboards and XIB files in iOS?
7.7.
7. Which method is called when an iOS app is about to enter the background?
7.8.
8. What is the purpose of Auto Layout in iOS?
7.9.
9. In iOS, which class is used to manage a table view?
7.10.
10. What is Core Data in iOS?
8.
Frequently Asked Questions
8.1.
Q. How to prepare for an iOS interview?
8.2.
Q. What is iOS design called?
8.3.
Q. How many layers are there in iOS?
9.
Conclusion
Last Updated: Sep 30, 2024
Easy

iOS Interview Questions

Introduction

iOS, Apple's mobile operating system, powers millions of devices worldwide, from iPhones and iPads to iPods and Apple Watches. With the increasing demand for mobile apps, skilled iOS developers have become highly sought after in the tech industry. Whether you're a professional iOS developer or just starting your journey, preparing for an interview can be daunting due to the vast array of topics covered in iOS development.

ios interview questions

What is iOS?

Before digging deep in the IOS Interview Questions articles, let us know first what is IOS specially. Apple Inc. conceived and developed the mobile operating system known as iOS specifically for its hardware. Many of the company's mobile devices, notably the iPhone, run on this operating system. The phrase also refers to the system software for iPads released before iPadOS, which debuted in 2019, and iPod Touch devices, which were phased out in the middle of 2022. After Android, it is the mobile operating system that is most extensively used worldwide.

Features of the iOS Platform

Some key features of the iOS Platform are:-

  • Design & User Interface (UI): The iOS is recognized for its slick and simple user interface, with fluid animations and user-friendly interactions
     
  • App Store: The Apple App Store offers a sizable ecosystem of programmes that have been selected and examined by Apple, ensuring that consumers only download safe and reliable software
     
  • Security: Data encryption, secure boot chains, app sandboxing, Face ID/Touch ID biometric authentication, and data encryption are just a few of the strong security features that make iOS so well-known
     
  • Upgrades and Support: Apple offers recurring iOS upgrades that include new features, bug fixes, and security patches, as well as long-term support for devices
     
  • iMessage and FaceTime: Apple devices may communicate for free using iMessage and FaceTime, which offer seamless messaging and video chatting for iOS users
     
  • Widgets and Customization: iOS enables users to add widgets to their home screens to provide quick access to important data and app features
     

Let's get started with IOS Interview Questions!

iOS Interview Questions for Freshers

1. Explain what TVMLKit is.

The combination of TVML, JavaScript, and tvOS apps is referred to as TVMLKit. 

2.  Define Bundle ID?

Apps for iOS and OS X both use the bundle ID. Every iOS application is uniquely defined by it. A bundle identifier can recognise any update to your application. 

3. Which framework is used to construct the application’s user interface?

Framework UIKIT. Views, windows, event processing, and drawing models are all rendered.

4. Explain what Code Coverage is?

We estimate the value of our unit tests using code coverage.

5. How can you open the Code Snippet Library in Xcode?

CMD+OTP+Cntrl+2

6. When is the category used?

It expands the Cocoa framework by adding new and related methods.

7. Explain what the Responder Chain is?

The hierarchy of objects that can react to events is described as a responder chain.

8. When is an app said to be not running the state?

When it is not launched or is stopped while running by the system, it is said.

9. Explain the object?

The majority of variables that are class types are considered objects. It might be a variable, data structure, method, or function.

10. When would you say that an app is in an active state?

In the foreground and accepting events, an app is considered to be in an active state.

iOS Interview Questions for Intermediate

11. Name some important data types found in objective-C?

There are four different types of data, which are as follows:

  • NSintegar
  • NSstring
  • CGfloat
  • Bool

12. What is iBeacon?

Mobile apps may now respond appropriately to signals from beacons in the real world thanks to iBeacon technology. There are two components to it: a broadcaster and a receiver.

13. What is Method Swizzling?

You can create code that can run before or after the original method by modifying the implementation of an existing domain using a method called Method Swizzling.

14.  What are the methods to achieve concurrency?

Concurrency can be achieved using the following methods:

  • Operation Queues
  • Dispatch queues
  • Threads

15. Which method can we use to perform final utilization before displaying the app to the user?

We can run the code for the first time using the method "application:didFinishLaunchingWithOptions" before showing the app to the user.

16. What does KVO stand for?

KVO, or key-value observing, allows a controller to keep track of changes in a property's value.

17. What is GCD?

Grand Central Dispatch (GCD) is a library that provides low-level and object-based APIs to carry out activities appropriately when managing threads.

18. What are the two different smart groups in Xcode?

It is divided into two parts:

  • Simple expression smart group
  • Simple filter smart group

19. What are the programming languages used for iOS development?

The programming languages used for iOS development are:

  • .NET
  • Swift
  • HTML5
  • C
  • Javascript

20.  What is ARC?

The technique of maintaining the lifespan of objects in Objective-C is defined by ARC (Automatic Reference Counting), a compiler-level feature.

iOS Interview Questions for Experienced

21. Which JSON framework does iOS support?

The SBJson framework is supported by iOS. To make handling JSON simpler, SBJson provides configurable APIs and extra control.

22. What is the difference between KVC and KVO?

User access to an object's properties is made possible by a process called KVC, or Key-Value Coding. In Swift, KVC enables object properties to be accessed at runtime with strings rather than knowing the property names statically throughout development. Key-Value Observing is also known as KVO. For tracking changes in programme state, it is employed. 

23. Explain the Observer Pattern?

We utilize the Observer pattern to notify other objects to state changes. The observer pattern is applied in two ways in Cocoa:

  • Notifications
  • Key-Value Observing (KVO)

24. Explain the Adapter Pattern?

A class that is an adapter accepts classes with unfavourable interfaces to work in a sink, wraps itself around an object, and provides a common interface to communicate with that object.

25. What is Operator Overloading?

The performance of current operators with already-existing types is improved by using operator overloading. Small symbols like +, *, and / are examples of operators.

26. What is the difference between atomic and nonatomic synthesized properties?

Atomic:

  • Not fast
  • Make certain the process is completed entirely by the CPU
  • Default behavior

Nonatomic:

  • Fast
  • Not being able to handle several queries at once.
  • Not default behavior

27. Define Cocoa/Cocoa touch?

It is used to create software codes that operate on iOS and are suitable with the iPad and iPhone. The objective-C programming language is used to create Cocoa Touch, which has a distinct set of graphical control elements than Cocoa.

28. What is the difference between Viewdidload and Viewdidappear? 

Viewdidload:

  • When it is loaded into memory, it is called.
  • If the data is relatively static and likely to change, Viewdidload can be used to load it.

Viewdidappear:

  • It is called when the view is visible and displayed on the device.
  • Any layout operations can be carried out, as well as drawing.

29. What methods can we follow to achieve concurrency in iOS?

The three methods are:

  • Dispatch queues
  • Operation queues
  • Threads

30. Explain layer objects in Swift.

Layer objects in Swift are data objects that represent the visual data on a UIView. Layer objects are used by views to render their content. We can add new layer objects to the interface to perform sophisticated animations and other features.

iOS MCQ

1. Which programming language is primarily used for iOS development?

A) Java
B) Kotlin
C) Swift
D) C#

Answer: C) Swift

2. What is the name of Apple's integrated development environment (IDE) for iOS app development?

A) Android Studio
B) Visual Studio
C) Eclipse
D) Xcode

Answer: D) Xcode

3. What is the purpose of the @IBOutlet keyword in iOS development?

A) To create a database connection
B) To connect interface elements to code
C) To define a function
D) To import external libraries

Answer: B) To connect interface elements to code

4. Which design pattern is most commonly used in iOS development?

A) Singleton
B) Model-View-Controller (MVC)
C) Observer
D) Factory

Answer: B) Model-View-Controller (MVC)

5. What is SwiftUI?

A) A database management tool
B) A framework for developing user interfaces
C) A library for handling network requests
D) A Swift package for cloud services

Answer: B) A framework for developing user interfaces

6. What is the default file format for storyboards and XIB files in iOS?

A) XML
B) JSON
C) YAML
D) CSV

Answer: A) XML

7. Which method is called when an iOS app is about to enter the background?

A) viewDidLoad
B) viewWillDisappear
C) applicationDidEnterBackground
D) applicationWillTerminate

Answer: C) applicationDidEnterBackground

8. What is the purpose of Auto Layout in iOS?

A) To manage memory usage
B) To control the app's background processes
C) To create flexible and responsive user interfaces
D) To manage data persistence

Answer: C) To create flexible and responsive user interfaces

9. In iOS, which class is used to manage a table view?

A) UICollectionView
B) UITableView
C) UIStackView
D) UIPickerView

Answer: B) UITableView

10. What is Core Data in iOS?

A) A framework for network communication
B) A framework for managing data persistence
C) A framework for creating animations
D) A framework for testing apps

Answer: B) A framework for managing data persistence

Frequently Asked Questions

Q. How to prepare for an iOS interview?

To prepare for an iOS interview, study iOS fundamentals, practice code, prepare for interview questions, build iOS project, understand app architecture, research the company project, and show caase your skills according to the need.

Q. What is iOS design called?

"UIKit" is a design framework for iOS. It is Apple's framework for developing user interfaces for iOS applications, offering a number of pre-designed components and tools to develop aesthetically pleasing and approachable user interfaces for iPhone and iPad apps.

Q. How many layers are there in iOS?

There are four main layers in iOS: Core OS (low-level functionality), Core Services (system services), Media layer, and Cocoa Touch (UI framework). Together, these layers form the structure on which iOS app development and functionality are built.

Conclusion

In this article, we have discussed iOS Interview Questions. Preparing for an iOS developer interview requires a solid understanding of fundamental and advanced iOS development concepts. From programming languages like Swift and Objective-C, to frameworks like UIKit and SwiftUI, mastering these areas is key to standing out in the competitive job market. In addition to technical skills, understanding design patterns, app lifecycle management, and Apple's ecosystem will help you succeed.

We hope that IOS Interview Questions blog has helped you enhance your preparation for IOS Interview Questions and if you would like to learn more, see

  1. iOS App Development Introduction and Features
  2. iOS vs. Android development
  3. iOS Development Basics

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