40 Common iOS Interview Questions (With Sample Answers)
By Indeed Editorial Team
Published 16 May 2022
The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.
Hiring managers ask different types of questions to test the skills and expertise of iOS programmers. These questions seek to evaluate your technical skills and soft skills, such as problem-solving abilities. Preparing answers to some common iOS questions can help software developers improve their chances of success in an interview. In this article, we share some frequently asked iOS interview questions and discuss a few sample answers to help you make a favourable impression in your next job interview.
10 iOS interview questions with sample answers
Here are some popular iOS interview questions with sample answers to help you prepare for your next interview:
1. What are the different states of an iOS application?
An interviewer may use this question to test your basic knowledge of iOS systems. In your response, you can describe the different states in which an iOS application can exist and explain them in detail if required.
Example: "There are a total of five states of an iOS application. The not running state is when the user doesn't launch the application and the system doesn't terminate it either. In the inactive state, the application keeps running in the foreground but isn't able to refresh automatically. Conversely, in the active state, the application runs in the foreground and refreshes automatically. In the background state, the app keeps running in the background while executing code. In the suspended state, the app stays in the memory of the device but isn't executing any code."
2. Why is React Native compatible with iOS applications?
In this question, the hiring manager wants to test your knowledge of different programming languages effective for iOS. You can explain why programmers prefer React Native for iOS application development in your answer. You can also discuss the specific situations where you can choose it over other programming languages.
3. List the four important data types in Objective-C.
As a developer, knowing Objective-C is important, as it's an essential programming language for iOS applications. Through this question, the interviewer is trying to assess your knowledge of the language. You can simply state all the data types in your response.
Example: "Data types help declare variables and functions of different types. The four types of data types in Objective-C include the NSString which represents a string and CGfloat, which represents a floating-point value. The other two are NSInteger, which represents an integer and Bool, which represents a boolean."
4. Which JSON framework does iOS support?
The interviewer wants to assess your knowledge of using different frameworks compatible with iOS. In your response, you can mention and explain the JSON framework supported by iOS and explain some of its benefits.
Example: "iOS supports the SBJson framework. In addition to being lightweight, humans and computers find it easy to read this framework. It's a JSON parser and Objective-C generator. Handling JSON also becomes easier when using SBJson's flexible APIs. It also offers a higher degree of control."
5. Define and explain the function of iBeacons.
iBeacons enables devices to interact with beacon signals. They help personalise the user experience and recommendations. The interviewer wants to evaluate whether you understand the technology and have experience working with it. In your response, you can explain iBeacons and mention if your previous projects required you to use the technology.
Example: "iBeacons helps mobile applications communicate with signals originating from beacons in the real world. Beacons are tiny bluetooth devices that continuously transmit signals to be read by devices and applications. iBeacon allows applications to gather relevant user data and deliver hyper-personalised content and experiences based on location. In one of my previous projects, my team worked on optimising iBeacon's functionality and relevance of recommendations."
6. Explain the function of layer objects.
Interviewers ask this question to assess your experience and expertise. You can define layer objects and explain how to use them in your answer.
Example: "Layer objects are simply data objects representing visual content. They're often used for content rendering. You can also add customised layer objects for different purposes, such as implementing a complex animation or adding any other type of special effect in the application."
7. Which one would you prefer between nonatomic and atomic properties?
Interviews can ask this question to determine how much practical experience you have working on iOS platforms and applications. In response to the question, you can explain these properties and how they're different.
Example: "Atomic properties always give back a fully initialised object, but this can impact performance. When it comes to a property that has no risk of initialising value, I would set it to nonatomic. This can help improve the performance, even if slightly."
8. Distinguish between a dictionary and an array.
This is a relatively easy iOS question that the interviewer may ask to test your foundational knowledge. You can describe both these in your response and explain how they're different.
Example: "You can read both arrays and dictionaries sequentially, but the difference is in how you access data. While you can access an array using the index of each element, accessing a dictionary requires something you define, like strings. Arrays also maintain order among objects, whereas dictionaries don't."
9. What are some common UI elements, and how can you add them to an iOS app?
This is another question to evaluate your fundamental iOS skills and knowledge. There are several elements that you can describe in your response to this question. Make sure you also explain how to add them.
Example: "Some common UI elements in iOS apps are buttons, images and labels. Essentially, any element visible in the app is a UI element. These elements can be interactive or static. In iOS apps, you can add UI elements using Xcode's interface builder. You can also code them and lay them out using NSLLayoutConstraints and Auto Layout."
10. How would you identify and fix an issue if a new app is crashing frequently?
This is a common question to assess your problem-solving skills and experience in handling app issues. In your response, you can describe a general method to identify and isolate a bug and suggest troubleshooting solutions for problems like crashing or freezing. Make sure you give a sequential answer that highlights a systematic approach.
Example: "After checking the iOS version and device specification, I would gather information about the issue to reproduce the issue. Accessing device logs can also help understand the problem better. This can help identify the nature of the issue and conduct a unit test to start the debugging process. Bug reporting and debugging tools can be beneficial in this process, as they can help identify different types of errors."
10 general iOS questions
Here are some generic interview questions about iOS applications and their architecture:
Briefly explain the architecture of iOS applications.
What are the main features of the iOS platform?
What are some tech websites, blogs and podcasts you follow?
Why did you become an iOS developer?
What are the programming languages used for iOS programming?
Explain the difference between App ID and Bundle ID.
How are strong, weak, read-only and copy different?
Define enumerations in Swift.
What are some benefits of a guard statement?
Explain the process of testing an application before its launch.
10 iOS questions about experience and specialisation
Recruiters can ask the following questions to assess your experience in iOS programming:
What type of projects and applications have you worked on in your career?
How do you overcome professional challenges?
What would you do if you didn't agree if the project manager's approach for a specific task?
Have you led the development of an iOS application?
Do you feel comfortable working in a team or individually?
Are you an expert in any of the iOS programming languages?
What would you consider being your best iOS-related skill?
What's the most challenging part of working with iOS-based platforms?
What's the most important programming lesson you've learned in your career?
What professional accomplishment gives you the most pride?
10 advanced iOS questions
Here are some in-depth iOS interview questions that hiring managers may ask:
Differentiate between synchronous and asynchronous tasks.
What's an ABI?
What's the process you follow to prioritise usability during designing?
Explain the most prominent difference between BDD and TDD.
Describe all the possible annotations available in Objective-C.
What's a bounding box?
What's the meaning and purpose of deep linking in iOS?
Define ARC or automatic reference counting.
Explain the different methods to achieve concurrency.
What are lazy properties in iOS?
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