Question 1
Difficulty: medium
How do you structure a Swift app so it stays maintainable as it grows?
Sample answer
I usually start by separating responsibilities very early, even in smaller apps. In a Swift project, I prefer a layered approach where views stay focused on presentation, view models handle state and user interactions, and services manage networking or persistence. That keeps the code easier to test and avoids turning controllers into giant catch-all files. I also pay attention to naming, file organization, and protocol-driven design so components are loosely coupled. If the app is expected to grow, I’ll set up dependency injection from the beginning and define clear boundaries between features. I’m also careful about keeping reusable utilities small and focused instead of creating one oversized helper layer. In practice, this makes onboarding easier for other developers and reduces regression risk when features change. Good structure saves time later, especially when deadlines get tight and multiple people are touching the same codebase.
Question 2
Difficulty: hard
Can you explain how you handle memory management in Swift, especially with closures and reference cycles?
Sample answer
I pay close attention to memory management because retain cycles can be subtle in Swift. My first step is understanding ownership: when an object should stay alive, and when it should be released. I use weak or unowned references only when I’m sure the lifecycle supports it, because choosing the wrong one can create crashes or hidden bugs. Closures are a common source of issues, especially when a view controller captures self while also being retained by a network callback, timer, or Combine subscription. In those cases, I typically capture self weakly, then unwrap it safely inside the closure. I also watch for delegates, completion handlers, and long-lived publishers. When debugging, I use Xcode’s memory graph and Instruments to confirm whether objects are being deallocated properly. I see memory management as part of code quality, not just a debugging task after the fact.
Question 3
Difficulty: medium
Tell me about a time you fixed a difficult bug in an iOS app.
Sample answer
In one project, we had a bug where a screen would occasionally show stale data after the user returned from editing an item. It didn’t happen every time, which made it hard to reproduce. I traced the issue to a combination of local caching and asynchronous updates that were completing out of order. The UI was rendering before the freshest data had arrived, so users sometimes saw an older version of the model. I added logging around the state transitions, reproduced the timing issue more reliably, and then adjusted the flow so the screen waited for the correct source of truth before updating. I also tightened the refresh logic so the view model emitted a single, predictable state instead of multiple partial ones. After the fix, we added a test around the state sequence to prevent regression. That experience reinforced how important it is to think in terms of data flow, not just UI symptoms.
Question 4
Difficulty: medium
How do you decide between using UIKit and SwiftUI in a new project?
Sample answer
I make that decision based on product needs, team experience, and the maturity of the feature set. If the app is greenfield and the UI is mostly standard, SwiftUI can be a great choice because it speeds up iteration, improves readability, and fits well with modern state-driven development. On the other hand, if the project depends on complex navigation, deep custom interactions, or needs to integrate with an existing UIKit codebase, UIKit may be the safer option or the right foundation for part of the app. I also consider deployment targets, because that affects what APIs are available and how much conditional work we need to maintain. In many real-world cases, I think hybrid is the most practical answer. I’m comfortable bridging between the two frameworks, so I focus on picking the tool that reduces risk and supports maintainability, rather than choosing based on preference alone.
Question 5
Difficulty: medium
How do you approach writing unit tests for Swift code?
Sample answer
I like unit tests to validate business logic, state transitions, and edge cases that are easy to break during refactoring. When I write Swift code, I try to keep it testable by isolating logic in view models, services, and pure functions instead of burying it inside UI code. That usually makes tests straightforward and fast. I focus on testing behavior rather than implementation details, so the test remains useful even when the code changes internally. For example, if a service returns mapped results from an API response, I’ll test success, decoding failures, and empty states. If a view model manages loading and error states, I’ll test the sequence of emitted states and verify the correct action is triggered. I also like using mocks or stubs for network and persistence dependencies, but I keep them simple so the test suite stays easy to understand. My goal is to make tests a support system for development, not a burden.
Question 6
Difficulty: hard
How would you improve the performance of a Swift app that feels slow when opening a screen?
Sample answer
I’d start by measuring before changing anything, because performance issues often turn out to be different from what they first look like. I’d use Instruments, Time Profiler, and Xcode’s debugging tools to identify whether the delay comes from main-thread work, image loading, data parsing, or excessive layout passes. On the code side, I’d look for expensive synchronous tasks happening during screen setup, such as JSON decoding, database queries, or formatting large datasets on the main thread. I’d also review whether the screen is doing too much during view lifecycle methods and whether anything can be deferred until after the first render. If images are involved, I’d check caching and resizing strategy. If it’s a table or collection view, I’d look at cell reuse, prefetching, and how much work happens during configuration. My general approach is to reduce main-thread pressure, simplify startup work, and verify each change with profiling so we improve real user experience instead of guessing.
Question 7
Difficulty: easy
Describe a time you had to work with designers or product managers to clarify requirements.
Sample answer
I’ve found that the best results come when I treat design and product conversations as part of development, not as a handoff. On one project, the initial spec for a feature looked simple, but once we discussed user flows, we realized there were several edge cases around loading, empty states, and partial failures. Instead of building from the first version of the ticket, I set up a short review with the designer and product manager and walked through the expected user experience step by step. That helped us define what should happen when data is delayed, how the screen should behave on smaller devices, and which errors needed a dedicated message. We ended up saving time because I didn’t have to guess, and they didn’t have to keep revisiting the feature later. I try to ask focused questions early, repeat back what I heard, and confirm assumptions before coding. That keeps delivery smoother and reduces rework.
Question 8
Difficulty: medium
How do you handle API integration in a Swift app, including errors and decoding?
Sample answer
When I integrate an API, I usually design the networking layer to be predictable and easy to extend. I define clear request and response models, keep endpoint logic centralized, and separate transport concerns from business logic. For decoding, I prefer using Codable where it fits, but I still inspect the actual payloads carefully because APIs often have inconsistencies or optional fields that need thoughtful handling. On the error side, I don’t treat all failures the same. I distinguish between connectivity problems, server-side responses, decoding issues, and app-level validation so the UI can react appropriately. I also make sure the app can show useful feedback to the user instead of a generic failure message. If the API is unstable or evolving, I add logging and make the model layer resilient to missing or unexpected values. A clean integration is not just about getting data in; it’s about making the app behave gracefully when the network or backend doesn’t cooperate.
Question 9
Difficulty: hard
What’s your approach to using async/await in Swift?
Sample answer
I like async/await because it makes asynchronous code easier to read and reason about than deeply nested callbacks. My approach is to use it where it improves clarity, especially for networking, database calls, and other tasks that naturally happen in sequence. I pay close attention to structured concurrency so I can keep task lifecycles manageable and avoid runaway background work. I also think about cancellation, because users navigate away quickly and we shouldn’t keep doing unnecessary work for a screen that is no longer visible. When a task affects the UI, I make sure state updates happen on the main actor where appropriate. I’m careful not to overuse concurrency just because it’s available; if a simple synchronous path is clearer, I keep it simple. The main value for me is that async/await makes intent obvious, which helps reduce bugs, improves testability, and makes the code easier for other developers to maintain.
Question 10
Difficulty: easy
How do you contribute to code quality and team standards as a Swift developer?
Sample answer
I try to raise code quality in practical ways that help the whole team, not just by enforcing rules. That starts with writing code that is readable, small in scope, and easy to change. I’m consistent about formatting, naming, and keeping functions focused so reviews stay efficient. I also like to review pull requests with an eye toward edge cases, test coverage, and long-term maintainability, not just whether the feature works on my machine. If I notice repeated patterns or recurring bugs, I’ll suggest a shared utility, a better abstraction, or a team convention so the problem doesn’t keep coming back. I’m comfortable giving and receiving feedback respectfully, and I think strong engineering teams improve when people can challenge ideas without making it personal. In practice, my goal is to make the codebase more predictable over time, because predictable code is easier to ship, debug, and evolve under pressure.
