The Ultimate iOS Interview Guide: 16 Comprehensive Questions from Beginner to Senior Level
Hello everyone,
Are you stepping into the dynamic world of iOS development, or maybe, are you looking to polish your knowledge and climb up the professional ladder? No matter where you are in your journey, it’s always a good idea to be prepared for what’s coming, and interviews can often pose some tricky challenges. We all know that knowledge is the key, but having the right set of questions can truly unlock a treasure of insights. In the exciting realm of iOS, staying updated and having an in-depth understanding is crucial. So, whether you are a newbie to iOS development or a seasoned professional, we’ve got something for everyone! Let’s dive right into this comprehensive guide on iOS interview questions, tailored just for you.
Beginner Level (0–1 years of experience)
Q1: What is the difference between classes and structs in Swift?
Answer: Both classes and structs are used to define custom data types in Swift, but there are several key differences between them. Structs are value types, meaning they are copied when assigned to a new variable or constant, or when they are passed to a function. Classes, however, are reference types — they are passed by reference, not value, which means if you change a property of a class instance, it would reflect in all other references of the same instance.
If you want to learn more detailed information on this subject, you can review my previous article:
Q2: What is Auto Layout?
Answer: Auto Layout is a system that allows developers to create an adaptive interface that responds appropriately to changes in screen size, orientation, and dynamic content. It works by creating a series of constraints that represent relationships between user interface elements.
Q3: Explain MVC, MVP, MVVM and VIPER architecture.
Answer: These are design patterns used in iOS development to organize code and separate responsibilities:
- MVC: Model-View-Controller. The Model represents the data and the business logic. The View displays the data. The Controller mediates between the Model and the View.
- MVP: Model-View-Presenter. It’s similar to MVC but with a more active Presenter.
- MVVM: Model-View-ViewModel. The ViewModel transforms data from the Model to values that can be displayed in a View.
- VIPER: View, Interactor, Presenter, Entity, and Router. This is a design pattern that implements the Single Responsibility Principle to create a clean and modular iOS architecture.
Q4: What is ARC in Swift?
Answer: ARC, or Automatic Reference Counting, is a system that tracks and manages your app’s memory usage. ARC automatically frees up the memory used by class instances when those instances are no longer needed.
Q5: What is a protocol in Swift?
Answer: A protocol defines a blueprint of methods, properties, and other requirements suitable for a particular task. Protocols can be adopted by classes, structures, and enumerations to provide an actual implementation of those requirements.
Intermediate Level (1–3 years of experience)
Q6: What is the difference between “weak” and “strong” in Swift?
Answer: “Weak” and “strong” refer to reference types in Swift. A “strong” reference is the default type, ensuring that an object cannot be destroyed as long as there is a strong reference to it. “Weak” references, on the other hand, do not prevent ARC from disposing of the referenced object. This is typically used to prevent retain cycles in closures and classes.
Q7: Explain the concept of optional in Swift.
Answer: Optionals in Swift are used to handle the absence of a value. Optionals are saying either “there is a value, and it equals x” or “there isn’t a value at all”. They are used when a variable might not have a value, i.e., the value could be nil.
Q8: How can you manage dependencies in iOS?
Answer: Dependencies can be managed in iOS projects using tools like CocoaPods and Swift Package Manager. These tools allow you to specify external libraries or packages that your project relies on, and they handle the process of fetching and integrating that code into your project.
Q9: What are GCD and OperationQueue?
Answer: Grand Central Dispatch (GCD) and OperationQueue are both used for managing concurrent operations but they are used in slightly different scenarios. GCD is a low-level C-based API that enables you to execute tasks concurrently. OperationQueue, on the other hand, is a higher-level abstraction based on GCD. It’s an Objective-C API that provides more control and added functionality, such as adding operation dependencies.
Q10: What are SwiftUI and UIKit, and how do they differ?
Answer: SwiftUI and UIKit are both used for building user interfaces in iOS. UIKit, introduced with the first version of iOS, is a mature and feature-rich framework but can be verbose and complex. SwiftUI, introduced in iOS 13, simplifies UI development with a declarative approach, reducing the amount of code required. However, it’s only supported on iOS 13 and later.
Mastering these questions and concepts is sure to give you a competitive edge in your upcoming iOS developer interviews. Whether you’re a beginner or an experienced developer, brushing up on these topics can only elevate your understanding of iOS development and make you a more appealing candidate to prospective employers.
Senior Level (4+ years of experience)
Q11: How does memory management work in Swift?
Answer: Swift uses Automatic Reference Counting (ARC) for memory management. Each time you create a new instance of a class, ARC allocates a chunk of memory to store information about that instance. This information includes the type of instance, its properties, and any methods it has. When an instance is no longer needed, ARC frees up the memory used by that instance so it can be used for other purposes.
Q12: Can you explain how error handling works in Swift?
Answer: Swift provides first-class support for throwing, catching, propagating, and manipulating recoverable errors at runtime. Errors are represented by values of types conforming to the Error protocol. Swift’s try/catch syntax is used to handle errors in a clear and expressive way.
Q13: What is the role of an AppDelegate in an iOS application?
Answer: AppDelegate is a central component of most apps and works closely with the app’s lifecycle. It’s responsible for events such as the launch of the application, its termination, transition to the background, and more.
Q14: How does Swift handle type safety and type inference?
Answer: Swift is a statically typed language which means it performs type checks before program execution, thus preventing type-mismatch errors. Swift also supports type inference. Even if you don’t specify the type of value you’re working with, Swift uses type inference to work out the appropriate type.
Q15: Can you describe MVVM and how it differs from MVC?
Answer: MVVM (Model-View-ViewModel) is a design pattern where the Model represents the data, the View is an interface that displays the data, and the ViewModel is a link between the Model and the View. Unlike MVC, in MVVM, ViewModel transforms the Model data into values that can be displayed on a View. This helps to keep the ViewController slim and improves the separation of concerns.
Q16: How would you go about performance tuning in iOS?
Answer: Performance tuning in iOS involves techniques such as lazy loading, caching, optimizing image sizes and formats, efficient use of threads, and avoiding memory leaks with careful use of strong and weak references.
Well, that’s a wrap, folks!
We’ve journeyed together from the very basics to the advanced depths of iOS development, exploring interview questions that span across different levels of expertise. We hope this guide provides you with a sense of confidence and clarity as you venture into your next interview. Remember, beyond the technical knowledge, your passion for learning, problem-solving skills, and adaptability in this ever-evolving field are what truly make you stand out. Keep exploring, keep growing, and above all, enjoy the process.
Thank you for joining me in this journey. We’d love to hear about your experiences and answer any other queries you might have. Stay tuned for more insights and happy coding!
Feel free to reach out, and until next time, keep innovating!
