iOS Developer
Interview Questions

Suggested answer:

• Situation: In my previous role at XYZ Tech, I was part of a versatile team responsible for developing a suite of apps for financial institutions.


• Task: I was assigned to create a secure and user-friendly mobile banking app, a complex task due to the number of features it needed and its required compliance with various financial regulations.


• Action: Utilizing my robust knowledge of iOS development, I was involved in every aspect of the app's creation, from initial conceptualization to final testing. I used Swift as the primary programming language due to its scalability and safety features.


• Result: The app was a success, receiving positive reviews for its ease of use, sleek design, and feature-rich services. It currently has over a million downloads in the App Store.

Suggested answer:

• Situation: As an iOS developer for the past five years, I've had the opportunity to work with both Swift and Objective-C.


• Task: In one project, we had to choose between Swift and Objective-C for the development of a health and wellness application.


• Action: I recommended Swift, which I prefer for several reasons: it's more modern, offers safer programming constructs, and allows for quicker development cycles. I led the project, leveraging Swift's powerful features to create a robust and responsive app.


• Result: The app was well-received, achieving a 4.5-star rating in the App Store within a month of its release. The speed of development and the security offered by Swift were critical to this success.

Suggested answer:

• Situation: In a past role at ABC Company, I was the lead developer for an eCommerce app.


• Task: I needed to design a user interface that was not only aesthetically pleasing but also adhered to Apple's design principles and interface guidelines.


• Action: I deeply familiarized myself with Apple's Human Interface Guidelines to ensure our design was both intuitive and compliant. I led workshops with my team to discuss these guidelines and incorporate them into our design.


• Result: Our application was praised for its intuitive design and smooth user experience. It was even featured in the "New Apps We Love" section on the App Store.

Suggested answer:

• Situation: At my previous job, we were developing a fitness app that allowed users to track their exercise routines, diets, and progress.


• Task: My task was to structure the app in a way that allowed for code reusability, simplified modification, and better data handling.


• Action: To accomplish this, I implemented the Model-View-Controller (MVC) architecture. This allowed me to segregate the application's data, user interface, and control logic effectively, enhancing the readability and maintainability of the code.


• Result: The app was successfully launched with positive feedback about its performance and user experience. The use of MVC also allowed us to add new features efficiently and fix bugs promptly.

Suggested answer:

• Situation: I was working on a photo-editing app at my previous company, and we faced memory-related issues due to the size and quantity of the images being processed.


• Task: I was tasked with identifying and resolving these memory issues to prevent app crashes and slow performance.


• Action: I used Instruments in Xcode to profile the app and pinpoint the memory leaks and heavy memory usages. I fixed these issues by optimizing our image handling and implementing autorelease pools to better manage memory.


• Result: These fixes greatly improved the app's performance, resulting in a smoother user experience and leading to a substantial decrease in app crashes reported.

Suggested answer:

• Situation: During my tenure at TechCompany, we developed a note-taking app that needed to save and retrieve user data effectively.


• Task: I was tasked with implementing a reliable and efficient persistence framework to handle the storage and retrieval of notes.


• Action: I decided to use Core Data due to its tight integration with iOS and its excellent performance for our use case. I designed a scalable data model and implemented efficient fetch requests to handle the app's data needs.


• Result: The note-taking app worked flawlessly, providing users with fast and reliable access to their notes. User reviews praised the app's responsiveness and reliability, contributing to a high overall rating in the App Store.

Suggested answer:

• Situation: At XYZ Solutions, we developed an app that provided real-time updates on local events. We noticed that the user interface appeared differently on various iOS devices, impacting user experience negatively.


• Task: My role was to ensure the app's uniform functionality and visual consistency across all iOS devices and versions.


• Action: I used Auto Layout for designing flexible and adaptable user interfaces and extensively tested the app on different devices and simulator configurations. For handling different iOS versions, I used version checks and conditional coding to ensure backwards compatibility.


• Result: The modifications ensured the app looked and functioned consistently on all devices and iOS versions, enhancing our users' experience and leading to an increase in positive reviews on the App Store.

Suggested answer:

• Situation: During my time at ABC Apps, we created a news aggregation app where users faced slow loading times due to constant data retrieval from the server.


• Task: I was responsible for implementing a strategy to reduce loading times and provide a smoother user experience.


• Action: I implemented a data caching strategy, storing frequently accessed data locally. I used the URLSession and NSCache APIs for fetching and caching data, respectively, and ensured data validity by implementing appropriate cache eviction strategies.


• Result: This significantly reduced loading times, improved app responsiveness, and reduced network data usage, contributing to a more seamless and user-friendly experience.

Suggested answer:

• Situation: In a previous role, we were developing an e-commerce app which needed to fetch product data from the company's server.


• Task: My task was to handle the API calls necessary for retrieving and updating data between the app and the server.


• Action: I used URLSession for making RESTful API calls. I implemented both GET and POST requests for retrieving and updating product data. I ensured error handling was in place for failed requests and applied best practices for parsing the received JSON data.


• Result: The successful implementation of APIs provided real-time, reliable product data to our users. This effort was instrumental in delivering a smooth, functional e-commerce experience and contributed to the app's overall success.

Suggested answer:

• Situation: At my previous position in StartApp Co., we were working on a major revamp of our flagship application to improve user experience and incorporate user feedback.


• Task: As the lead iOS developer, my task was to oversee the transition from UIKit to SwiftUI for our application's UI development.


• Action: I began with creating SwiftUI versions of smaller, less complex views, gradually moving to more complex ones. I leveraged SwiftUI's powerful and intuitive tools, such as declarative syntax and live previews, to accelerate the development process. The transition was done incrementally to ensure app stability.


• Result: The successful transition to SwiftUI resulted in a more intuitive and user-friendly application. User feedback post-launch was overwhelmingly positive, indicating an improvement in user satisfaction and increased app usage.

Suggested answer:

• Situation: In my role at ByteSphere Tech, I was part of a team responsible for a mobile banking application. Ensuring high performance and quality was essential due to the critical nature of the application.


• Task: It was my duty to implement and maintain the highest possible quality and performance standards for the application.


• Action: I ensured efficient code by regularly profiling the application using Instruments. To ensure quality, I advocated for and implemented rigorous unit and UI testing using XCTest and XCUITest. I also initiated code reviews to promote best practices and catch potential issues early.


• Result: Through these measures, we maintained high performance and robustness of the app, keeping crash rates low and user ratings high on the App Store.

Suggested answer:

• Situation: At my previous company, we were developing a health app that stored sensitive user data.


• Task: As an iOS developer, it was my responsibility to ensure the highest level of security for user data.


• Action: I implemented several security measures, such as using Keychain for storing sensitive data, employing secure coding practices to prevent injection attacks, and utilizing HTTPS for network communications. Additionally, I ensured data encryption at rest and in transit, and implemented Touch ID/Face ID authentication for added security.


• Result: These measures significantly enhanced the security of our application, providing users with peace of mind and confidence in our commitment to protecting their sensitive data. Our application received positive reviews for its robust security features, resulting in an increase in user trust and app downloads.

Suggested answer:

• Situation: While working for TechStorm Corp, one of our clients was a popular e-commerce company wanting to increase user engagement.


• Task: I was tasked with implementing push notifications to alert users of special offers, promotions, and delivery updates.


• Action: I integrated Apple Push Notification Service (APNs) into the application. I also made sure to provide users with customization options so they could choose the types of notifications they wanted to receive. This was done to prevent notification fatigue and ensure a positive user experience.


• Result: With these tailored notifications, we saw a significant increase in user engagement, with a considerable uptick in app opens from push notifications. The client was delighted with the outcome, which improved their sales and user retention rate.

Suggested answer:

• Situation: At my last job, we were developing a new social networking app, and during the beta testing phase, we encountered a recurring crash.


• Task: As the team's lead iOS developer, my job was to locate the source of the bug and fix it.


• Action: Using the information from the crash reports and Xcode's debugger, I started by replicating the crash to better understand the issue. I then performed step-by-step debugging, employing breakpoints and inspecting variable values to locate the source of the problem. It turned out to be an unhandled nil value causing the crash.


• Result: After fixing the issue and adding appropriate nil handling, the crashes were resolved. This experience has since shaped my approach to debugging, focusing on detailed crash report analysis, reproducing the error, and systematic troubleshooting.

Suggested answer:

• Situation: Suppose I've joined your team as a new iOS developer, and I notice that there are areas in the codebase that could benefit from refactoring and optimization.


• Task: My task would be to contribute to the development and improvement of your existing iOS applications.


• Action: I would initiate a conversation with the team about potential improvements and present my ideas for optimization, backed by my analysis and benchmarking. For example, replacing redundant code with reusable components, or migrating some UIKit components to SwiftUI for better performance and maintainability. I would also emphasize the importance of code reviews and testing to maintain code quality.


• Result: The result of such an initiative would be an improved, efficient, and easily maintainable codebase, leading to faster feature development, fewer bugs, and, ultimately, a better product for end users.