Preparing for a technical iOS job interview
with over 300 questions & answers
About this book
Having been a freelance iOS dev for over a decade now, I participated in quite a few hiring interviews for various projects and have also been in a position of leading the technical interviews myself.
With this book, I want to give you a guide for technical iOS questions you might be asked in such an interview. These questions aren’t meant to be memorized or used as a checklist of must-know topics. Instead, think of them as guiding stars, designed to help you reflect on your knowledge, spark curiosity, and uncover areas you may want to explore more deeply.
Some questions will feel immediately relevant. Others might dip into edge cases or advanced areas. Not every role requires mastery of every topic, and you are certainly not expected to know everything.
That said, while iOS development, and software development in general, is more about understanding and critical thinking than having all the answers, it can still be calming to refresh your memory before an interview. Skimming through questions like these can warm up your technical thinking, surface things you already know, and help you walk into the conversation with more confidence. At least, I hope it does.
I wish you a happy learning, and may your journey in iOS development be as exciting as it is rewarding.
Structure of this book
Each chapter starts with a questions overview that allows you to check your knowledge without seeing the answers. All questions are numerated so you can quickly find the answer when needed. The following topics are covered in this book:
Swift
Being the main programming language for the iOS platform, a deep knowledge in Swift is expected from an iOS developer. This chapter provides questions and answers on Swift and general programming language concepts.
SwiftUI
SwiftUI is Apple's main framework for building user interfaces for iOS. This chapter provides questions and answers on the main aspects of SwiftUI.
Xcode
Being the main iOS development tool, a confident usage of Xcode is expected from an iOS developer. This chapter provides questions and answers on working and debugging with Xcode.
Combine
The Combine framework is Apple's native solution for handling asynchronous events and data streams in Swift. It enables developers to write functional reactive code, streamlining tasks like chaining, transforming, and combining data. This chapter provides questions and answers on Combine and on functional reactive programming concepts in general.
Server Communication
Server communication is part of almost every iOS application. This chapter provides questions and answers on general computer networking concepts and on specific iOS networking topics.
Concurrency
This chapter focuses on Swift's concurrency model with async/await. It also provides questions and answers on more low-level technologies like Grand Central Dispatch and Operations. Since they were used in iOS applications before async/await, knowledge around these technologies may be required for an iOS position.
Persisting Data
Persisting pieces of data is required in many applications. Apple offers solutions to store data for different scenarios. This chapter contains questions and answers on persistence technologies and frameworks such as File System, UserDefaults, SwiftData and Core Data.
Security
Many applications need to manage some kind of sensitive user data. To ensure a high level of security Apple provides different technologies to be used by developers. This chapter provides questions and answers on specific security-related iOS technologies such as keychain or shared web credentials, general cryptography concepts, and privacy-related requirements for apps and third-party SDKs.
Automated Testing
Testing is an important part in every software development process. Apple offers tools to write unit, UI and performance tests for iOS applications. This chapter provides questions and answers on general testing concepts and specific iOS testing tools.
Architecture & Design Patterns
Architectural principles and design patterns are the foundation of robust, maintainable, and scalable iOS applications. This chapter explores key architectural concepts and widely used design patterns in iOS development, providing practical examples and insights into their strengths and weaknesses.
Accessibility
Accessibility is a crucial aspect of iOS development that ensures an app can be used by people with disabilities. This chapter covers the fundamental concepts and implementation techniques for making iOS applications accessible to all users.
Dependency Management
Most iOS apps depend on code outside the app target itself. This can include Swift packages, binary SDKs, local modules, or older dependency managers such as CocoaPods and Carthage.
Dependencies can speed up development, but they also affect build times, app size, privacy, security, maintenance, and long-term flexibility. This chapter covers how dependencies work in modern iOS projects and what to consider when adding, updating, or relying on third-party code.
AI & Machine Learning
AI and machine learning are an increasingly important part of software development and engineering jobs. Machine learning techniques are used to build models that can learn patterns in data and make predictions, classifications, or generations without being explicitly programmed for every case.
On Apple platforms, this includes Apple Intelligence and the Foundation Models framework, classic machine learning workflows with Core ML and Create ML, and newer on-device AI capabilities with Core AI. This chapter starts with the AI and machine learning tools iOS developers are most likely to use in apps, then covers the machine learning concepts that are useful to know when working with these technologies.
Working with Legacy Code: UIKit
With SwiftUI pushing UIKit into the background since 2019, UIKit may still be part of existing iOS applications. A deep knowledge of UIKit may be required for an iOS position. This chapter provides questions and answers around key aspects of UIKit.
Working with Legacy Code: Objective-C
Objective-C is becoming more and more obsolete after Swift was released in 2014. However, with existing apps written in Objective-C still out there, knowledge on Objective-C may be required for an iOS position. This chapter provides questions and answers on Objective-C basics and the interoperability between Swift and Objective-C.