10 Common iOS Interview Questions (With Answers And Tips)

Updated 19 January 2023

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Understanding how to respond to some of the most asked iOS interview questions can help you succeed in an interview for an iOS developer position. Regardless of your background or work experience, your responses to interview questions are likely to influence the decision of the hiring manager. Being familiar with the type of questions that hiring managers may ask can be a significant advantage to help you impress hiring managers. In this article, we discuss some common iOS interview questions with their sample answers and offer some preparation tips to help you succeed in your iOS interview.

10 Common iOS Interview Questions With Sample Answers

Here are some potential iOS interview questions you may encounter during an interview:

1. Explain the major states of an iOS application.

This is a fundamental question that employers ask to find out your familiarity with the IOS app states. You can respond by simply describing each one. The interviewer may follow up with additional questions related to any of the states.

Example: “There are five major iOS application states. The first state is not running, it is when the user or any service has not launched the app. Then there is the inactive state when the app is running in the foreground but is not receiving current events and the active state for when the app is running in the foreground and is receiving events. This is the normal mode for foreground apps.

The last two are the background state, which means the app is in the background and executing code, and finally, the suspended state. A suspended app remains in memory but does not execute any code."

2. What is app ID in Swift?

App ID is an important concept for iOS developers. This is a question that employers often ask during iOS interviews. You can briefly define app ID and its uses to demonstrate your knowledge and show that you can use this system in the job role.

Example: “App ID is a unique identifier iOS uses to connect the application to the Apple push notification service, share keychain data between applications, and communicate with external hardware accessories that we want to pair with an iOS application.”

3. What is a bundle identifier in Xcode?

Employers often ask this question to assess your ability and level of understanding of bundle identifiers. Focus on answering questions by providing details about its use case. You can also provide a suitable example of your use of bundle identifiers in a project and its effect on the result.

Example: “A bundle identifier enables iOS and macOS to recognize application updates. Apple requires that the bundle ID is registered and unique to the app. We set these identifiers in Xcode during the app build. This identifier is application specific to either iOS or macOS.”

4. Which API would you consider most suitable for writing test scripts for an app's UI elements?

You can respond to this question in a variety of ways, depending on your preferred method. Try describing the entire scriptwriting and testing process in a concise manner. Sharing examples of past experiences using different APIs may be helpful.

Example: "I prefer to automate test procedures using the UI automation API and then run JavaScript test scripts that simulate user interaction with the app and return data to the host device."

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

Both are popular programming languages for developing iOS applications. While the interviewer may seek a concise definition of both, they can follow up by asking you to describe specific instances where you would choose one over the other. You can differentiate the two by illustrating examples of their use.

Example: "Objective-C is the fundamental programming language used to create applications for iOS and OS X. It is a superset of the C programming language, inheriting its syntax, primitive types, and flow control while adding syntax for class and method definition.

Swift is a cross-platform programming language that runs on iOS, macOS, watchOS, and tvOS. It uses C and Objective-C features but is a lot more compatible than C. Swift simplifies the code and increases the flexibility of programming."

6. Which framework do you prefer for developing an iOS application user interface?

A framework provides the infrastructure required for various applications. With this question, the interviewer may want to assess your understanding of the UI development for an iOS app. You can mention the UIKit framework and briefly explain its various uses.

Example: “I prefer UIKit framework as it provides the required infrastructure for your iOS or tvOS apps. It includes event handling, drawing model, windows, views, and controls specifically designed for a touch screen interface.”

7. What makes React native so effective on iOS?

The interviewer may wish to assess your knowledge of various programming languages used in iOS app development and determine whether you can identify which is the most appropriate in this particular scenario. Explain why React native is a good fit for iOS, but also why you would prefer it over Swift or another programming language.

Example: "By utilizing React native, we ensure the JavaScript builds the application logic and its UI is entirely native, avoiding the issues and compromises associated with HTML 5 UI. React also introduces a newer and more straightforward method to develop user interfaces by expressing them as functions of the current app state."

8. Explain how BDD and TDD differ?

Questions on similar concepts like this help an interviewer understand your skill level. By demonstrating how and when to use each statement, you confirm your experience with both. While answering this question, explain the difference concisely.

Example: “BDD stands for behavioral-driven development and TDD stands for test-driven development. The critical difference is in the scope. TDD is a method for software development, whereas BDD is for a team. TDD requires developers to write tests, whereas BDD requires users or testers to create automated specifications, which developers then connect to the code under test. TDD and BDD are effectively identical in small, co-located, developer-centric teams.”

9. What is the difference between Cocoa and Cocoa Touch?

Interviewers often ask this question to find out whether you are aware of the two framework collections. Apart from defining the two concepts, you could also state that Cocoa Touch is exclusive to iOS.

Example: "Cocoa and Cocoa Touch is the application development environments for OS X and iOS, respectively. Both Cocoa and Cocoa Touch include the Objective-C runtime and two core frameworks. Cocoa includes the Foundation and AppKit frameworks, which we use for developing applications that run on OS X. Cocoa Touch includes Foundation and UIKit frameworks for developing applications that run on iOS."

10. What is the lazy property in swift?

With this question, an employer may want to assess your understanding of efficient device resource usage. You can briefly explain the property, and mention its usefulness and previous experiences of implementing the same.

Example: “A lazy property is a property whose initial value isn't calculated until it is used for the first time. Developers can use this property in multiple ways, especially when the value is dependent on outside factors that are unknown. We denote a lazy stored property by adding the lazy modifier before its declaration.”

Tips To Prepare For An iOS Interview

Here are some tips you can consider while preparing for an iOS interview:

Build your story

The employer may ask you to tell about yourself and what got you into programming. Plan ahead of time to mention the different experiences that inspired you to pursue this career. A well-crafted answer to personal questions can often showcase your confidence and interest.

Know your workflow

The employer may ask multiple questions regarding your workflow as it would help them in assessing your knowledge and understanding of iOS app development. You can briefly mention the various tools and techniques you follow during the app developmental process. They may also ask follow-up questions regarding your choice of a tool or process over another, so consider exploring different options and finding your preferences.

Demonstrate your social skills

Although an employer may primarily seek to understand your programming skills, they also want to know how well you can work with a team on a day-to-day basis. The app development process involves multiple people working on the same project. Giving confident and open answers can show them you have a personality that can work well within a team.

Create a portfolio

iOS development is a skill that you can highlight using your past work experiences. Companies hiring app developers often expect a portfolio of projects you have worked on. You can start developing your portfolio independently by looking at some online design concepts and creating codes for them or seek professional internships that allow you to work on multiple projects.

Please note that none of the companies mentioned in this article are affiliated with Indeed.