Top 35+ iOS Interview Questions and Answers for 2024

This article lists some of the most commonly asked iOS interview questions for freshers and experienced candidates. This list of the most important iOS developer interview questions will help you succeed in your next interview.

Are you preparing to break into a career as an iOS developer? If yes, ease the stress and brush up on some skills you haven’t used in a while – you are all set to go. The demand for iOS developers is expected to increase due to the rapid adoption of iOS devices. Let’s look at some of the most important iOS interview questions, which will be a great self-test if you seek some practice for your iOS interview.

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Top iOS Interview Questions for 2024

Here is the list of the most commonly asked iOS developer interview questions and answers for freshers and experienced candidates.

Q1. What is ARC?

Ans. ARC (Automatic Reference Counting) is a compiler-level feature that defines the process of managing the lifetime of objects in objective-C.

Q2. Define Bundle ID?

Ans. The bundle ID is used for both OS X apps and iOS.  It uniquely defines every iOS application. A bundle identifier can recognize any update to your app.

Q3. Explain the Architecture of iOS.

The architecture of iOS comprises four main layers: the Core OS layer, the Core Services layer, the Media layer, and the Cocoa Touch layer.

Core OS layer: This is the lowest level of the iOS architecture and includes the kernel, device drivers, security features, and other low-level system services. The kernel manages hardware resources, such as the CPU, memory, and input/output devices.

Core Services layer: This layer provides a set of fundamental services that are used by other layers of the system, including networking, file access, and location services. It also includes frameworks for managing data, such as Core Data, and accessing system resources, such as the Address Book.

Media layer: This layer supports audio, video, and graphics. It includes the Core Audio, Core Video, and Core Animation frameworks, which provide powerful tools for managing multimedia content.

Cocoa Touch layer: This layer provides the user interface and application frameworks for building iOS apps. It includes the UIKit framework, which provides the basic building blocks for building app interfaces, such as buttons, text fields, and images. It also includes other frameworks for handling touch events, managing views, and accessing system services.

Q4. Name some important data types found in objective C?

Ans. There are four data types which are as follows:

• Bool
• CGfloat
• NSintegar
• NSstring

Q5. Define Cocoa/Cocoa touch?

Ans. It is used to build software codes for iOS for the iPad and iPhone. Cocoa Touch is written in the objective-C language and has a different set of graphical control elements to Cocoa.

Q6. What are the programming languages used for iOS development?

Ans. Programming languages used for iOS development are:

• HTML5
• .NET
• C
• Swift
• Javascript
• Objective-C
• Swift

Check out Swift programming languages courses

Q7. What are the methods to achieve concurrency?

Ans. The methods to achieve concurrency are:

• Dispatch queues
• Threads
• Operation Queues

Q8. What is the difference between Android and iOS?

Feature	Android	iOS
User Interface	Customizable with a range of UI options	Consistent and controlled by Apple
Device Fragmentation	Wide range of devices from various manufacturers	Limited range of devices from Apple
App Store	Google Play Store and other third-party app stores	Apple App Store only
Multitasking	Supports split-screen multitasking	Limited multitasking options
Default Apps	Users can set default apps for various functions	Default apps controlled by Apple
Customization	Allows users to customize their device with widgets and other third-party apps	Limited customization options
Security	The open-source nature can make it more vulnerable to malware and security issues	A closed-source system with a strict app review process for security
Cost	A range of devices available at different price points	Limited range of premium devices at higher price points
Programming Language	Java and Kotlin	Objective-C and Swift

Q9. What is the difference between atomic and nonatomic synthesized properties?

Ans. Atomic:

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

Nonatomic:

• Not default behaviour
• Faster
• Not able to deal with multiple requests at the same time

Q10. When is an app said to be not running the state?

Ans. It is said when it is not launched or gets terminated by the system while running.

Learn more about iOS, read our post – What is iOS App Development?

Q11. Explain the object.

Ans. Objects are mainly the variables that are of class types. It can be a function, method, data structure, or variable.

Q12. When would you say that an app is in an active state?

Ans. An app is said to be active when it accepts events and runs in the foreground.

Q13. Which framework is used to construct the application’s user interface?

Ans. UIKIT framework. It renders drawing models, windows, event handling, and views.

Q14. What is iBeacon?

Ans. iBeacon enables mobile apps to listen to signals from beacons in the physical world and respond accordingly. It comprises two parts: a broadcaster and a receiver.

Let’s take a look at some more iOS interview questions.

Q15. What is Method Swizzling?

Ans. Changing the implementation of an existing domain, Method Swizzling enables you to write that code that can be executed before or after the original method.

Let’s take a look at some more iOS interview questions.

Q16. When is the category used?

Ans. It is used to add a set of related methods and to add additional methods in the Cocoa framework.

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Q17. What is the difference between Viewdidload and Viewdidappear?

Ans. Viewdidload:

• It is called when it is loaded into memory.
• Data can be loaded in Viewdidload if it is fairly static and likely to change.

Viewdidappear:

• It is called when the view is visible and presented on the device.
• You can perform any layout functions or draw in the UI.

Q18. What does KVO stand for?

Ans. KVO stands for Key-Value Observing, which is a mechanism in the Apple development ecosystem for observing changes to the properties of an object. It is a way for one object to be notified when a property of another object changes without having to poll or check for updates constantly.

In iOS and macOS development, KVO is often used with other key Apple technologies, such as Core Data and Cocoa Bindings. It is a powerful tool for building responsive, data-driven applications that update user interfaces in real-time based on changes to the underlying data model.

Q19. Explain layer objects in Swift.

Ans. In Swift, layer objects are data objects representing visual content on UIView. Views use layer objects to render their content. We can add custom layer objects to the interface to implement complex animations and more.

Q20. What are the two different smart groups in Xcode?

Ans. Smart Groups are divided into two parts:

• Simple expression smart group
• Simple filter smart group

Q21. How can you open the Code Snippet Library in Xcode?

Ans. CMD+OTP+Cntrl+2

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Q22. Explain what TVMLKit is.

Ans. There is a link between JavaScript, TVML, and tvOS apps, which combines and is known as TVMLKit.

Q23. What is GCD?

Ans. GCD (Grand Central Dispatch) defines as a library that offers object-based and low-level API to execute tasks accordingly when managing threads.

Q24. Mention the features of iOS 14.

Ans. Following are the features of iOS 14:

• New App Library
• Home screen redesign
• No full-screen calls
• App Clips
• Translate app

Q25. What are the methods we can follow to achieve concurrency in iOS?

Ans. There are three methods we can follow to achieve concurrency in iOS:

• Operation queues
• Threads
• Dispatch queues

Q26. Which method can we use to perform final utilization before displaying the app to the user?

Ans. Before displaying the app to the user, we can use the method “application:didFinishLaunchingWithOptions” to execute the code for the first time.

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Q27. Explain what Code Coverage is?

Ans. Code coverage is used to calculate the value of our unit tests.

Q28. Explain what the Responder Chain is?

Ans. A Responder Chain is explained as the hierarchy of objects that have the opportunity to respond to events received.

Q29. What is Operator Overloading?

Ans. Operator overloading is used to work on how existing operators perform with types that already exist. Operators are those little symbols like +, *, and /.

You can also explore: Operator Overloading in C++ 

Q30. Why is the use of a design pattern in Linux?

Ans. Design patterns are used to solve common problems in software design. These design patterns use different templates to help you write code that is easy to understand. Look at some common Cocoa design patterns:

• Creational: Singleton.
• Behavioral: Observer, and, Memento
• Structural: Decorator, Adapter, Facade

Q31. Explain the Adapter Pattern?

Ans. An Adapter acknowledges classes with adverse interfaces to work in a sink and tie itself around an object and exposes a standard interface to interact with that object.

Q32. What is the difference between assign and retain keywords?

Ans. The assign keyword creates a reference from one object to another without increasing the source’s retain count. It assigns the directly to the instance variable and does not copy or retain it. The retain keyword creates a reference from one object to another. It increases the retention count of the source object.

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Q33. What is the difference between KVC and KVO?

Ans. KVC stands for Key-Value Coding, which enables users to access an object’s properties. In Swift, KVC allows object properties to be accessed at runtime with strings instead of knowing the property names statically at the time of development. KVO is short for Key-Value Observing. It is used for observing program state changes.

Q34. Explain the Observer Pattern.

Ans. The Observer pattern is used to notify other objects of any state changes. Cocoa uses the observer pattern in two ways: 

• Notifications
• Key-Value Observing (KVO)

Q35. Mention the Realm benefits?

Ans. Following are the Realm benefits:

• An open-source database framework.
• Zero copy object-store.
• Implemented from scratch.
• Fast.

Q36. Which JSON framework does iOS support?

Ans. iOS supports the SBJson framework. SBJson offers flexible APIs and additional control so that handling JSON becomes easier.

Q37. Name the APIs for battery-efficient location tracking.

Ans. It is one of the most popularly asked iOS interview questions.

The following are three types of APIs:

• Significant location changes: the location is delivered approximately every 500 meters (usually up to 1 km)
• Region monitoring tracks enter/exit events from circular regions with a radius equal to 100m or more. Region monitoring is the most precise API after GPS.
• Visit events: monitor place Visit events which are entered/exited from a place (home/office).

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Conclusion

We hope these top iOS interview questions and answers will improve your knowledge and help you crack any iOS job interview.