What Topics Do I Need to Study for an iOS Interview?
- Jul 18
- 16 min read
What Topics Do I Need to Study for an iOS Interview?
What Topics Do I Need to Study for an iOS Interview?
One of the most common questions developers ask when they begin preparing for an iOS interview is surprisingly difficult to answer.
"What exactly should I study?"
At first glance the answer seems obvious. Study Swift. Study SwiftUI. Revise UIKit. Read about networking, concurrency and memory management. The problem is that this advice isn't particularly useful because Swift itself is an enormous language and iOS development is an even larger subject. Without some structure it's very easy to jump from one tutorial to another, watch a few YouTube videos, read several blog posts and still finish the week feeling as though you haven't made much progress.
After speaking to many developers over the years, I think most people begin their interview preparation in the wrong place. They immediately start consuming information without first deciding how they're going to organise everything they learn. As a result, every interview feels like starting from the beginning again. They revise for a few weeks, attend the interview, return to work, and gradually forget many of the details they worked so hard to refresh. Six months later another interview appears on the horizon and the entire process repeats itself.
I believe there is a much better approach.
Rather than asking yourself what you should study first, ask yourself how you can build a resource that will help you prepare for every interview you attend throughout your career. Once you begin thinking this way, interview preparation changes from being a temporary activity into something that gradually becomes easier with every passing year.
Create Your Own Swift Revision Document
The first thing I recommend doing has nothing to do with reading Apple's documentation or downloading another course. Instead, create a document that belongs entirely to you.
It doesn't matter whether you prefer Markdown, Notion, Apple Notes, Obsidian or a simple text file stored in a Git repository. The format is largely irrelevant. What matters is that you have a single place where you can collect your knowledge as your career progresses.
This document should become your personal Swift revision handbook.
Every time you encounter an interview question that catches you by surprise, add it to the document. Every time you discover an explanation that finally makes a difficult concept easier to understand, write it down in your own words. If you produce a particularly nice piece of example code during a project, copy a simplified version into your notes. If somebody on your team explains ARC, actors or protocol extensions in a way that immediately makes sense, preserve that explanation before you forget it.
Over time this document begins to reflect your own journey as an iOS developer. It stops being somebody else's tutorial and becomes something considerably more valuable: a collection of knowledge that you have personally found useful.
This is one of the biggest differences between preparing for your first interview and preparing for your tenth. Experienced developers rarely need to learn Swift from the beginning again. More often, they simply need to reconnect with ideas they haven't thought about recently. Your revision document exists to make that process as quick and as painless as possible.
Your Goal Isn't to Rewrite Apple's Documentation
One mistake I think many developers make is trying to create comprehensive notes that explain every corner of the Swift language. This quickly becomes overwhelming and usually results in an unfinished document that nobody ever wants to revisit.
That isn't the goal.
Apple has already written an excellent reference for the Swift language. The purpose of your own document is different. It should contain the information that you are most likely to forget.
Perhaps that's a short explanation of how weak and unowned references differ. Maybe it's a reminder about the difference between map, compactMap and flatMap. It could be a small example showing how actors prevent data races, or a note explaining why structs exhibit value semantics while classes exhibit reference semantics.
Each topic only needs enough information to trigger your memory. Some sections might contain a few paragraphs, while others might consist of nothing more than a short code sample and a link back to Apple's documentation.
Think of the document as your own revision guide rather than a replacement for the official Swift book.
Organise Everything into Topics
Once you've created the document, begin adding headings for every topic that you believe could appear during an interview.
Don't worry if some sections remain empty initially. The objective isn't to complete the document in a single weekend. You're building something that should continue growing throughout your entire career.
A sensible starting point might include categories such as:
Collections
Arrays
Dictionaries
Sets
map
compactMap
flatMap
filter
reduce
sorted
Functions
Closures
Capture lists & their default behaviour
Tuples
Higher order functions
First class citizens
What is the functional programming paradigm?
Memory Management
Automatic Reference Counting (ARC)
Strong References
Weak References
Unowned References
Retain Cycles
Closure Capture
Copy-on-Write
Heap vs Stack
Value Types vs Reference Types
Swift Concurrency (Only if you already know it)
async/await
Tasks
Task Groups
Actors
Actor Isolation
MainActor
Sendable
Structured Concurrency
Detached Tasks
Cancellation
Continuations
Async Sequences
SwiftUI
State Management using reference types
View being nothing but a declarative set of instructions with access to possible shared state objects
Observable Objects
@State
@Binding
@Environment
@EnvironmentObject
Navigation
Lists
Architecture
What is MVC?
What is MVVM?
What is the Model?
Dependency Injection & IOC (Inversion Of Control)
Declarative programming paradigm
Imperative programming paradigm
Composition over inheritance
What is Layered architecture?
Draw the layered architecture of an iOS app
KISS, WET, DRY, Single Responsibility, SOLID (out-of-date now), Separation of Concerns (SoC), Fail Fast, Loosely coupled, tightly coupled.
Networking
URLSession
Codable
JSON Decoding
JSON Decoding with custom keys
Error Handling, throwing errors
Testing
How to Write basic Unit Tests in Xcode
This list might appear intimidating at first, but remember that you aren't expected to master every topic immediately. You're simply creating a framework that you can continue building over the coming months and years.
There are an enormous number of topics that could eventually find their way into your revision document. The goal isn't to write an entire programming book or produce a comprehensive reference for Swift. Instead, each heading should contain a concise explanation that refreshes your memory in a matter of seconds. Some topics may benefit from a small code snippet, while others might only require a short paragraph describing the concept in your own words.
Over time, your document may grow to cover well over one hundred topics, yet it should remain surprisingly quick to read. The aim is to create something you can comfortably work through in twenty or thirty minutes before an interview. Rather than trying to relearn Swift from scratch, you'll be reconnecting with knowledge you already possess.
When you eventually sit down in the interview and the discussion begins to flow naturally, you'll appreciate just how valuable this document has become. By revisiting a large number of concepts immediately beforehand, you've given yourself the opportunity to reactivate months or even years of accumulated knowledge. T
he document doesn't teach you Swift—it reminds you of everything you've already learned.
Allow the Document to Grow Naturally
One of the biggest advantages of maintaining your own revision document is that it never really reaches a finished state.
Imagine attending an interview where you're asked to explain retain cycles. Afterwards, regardless of whether you answered well or badly, spend half an hour improving the ARC section of your notes. Add a better explanation. Include a small example. Perhaps draw a simple diagram showing two objects holding strong references to one another.
A few months later you might be working on a project that makes extensive use of Swift Concurrency. During development you discover a particularly elegant explanation of actor isolation that finally helps everything click. Add that explanation to your document as well.
Perhaps somebody on your team introduces a cleaner way of structuring networking code using dependency injection. That's another opportunity to improve your notes.
The document slowly evolves alongside your career.
Eventually you stop thinking of interview preparation as a separate activity because you're constantly improving the very resource that helps you prepare.
Learn Through Experimentation
Reading about Swift is important, but reading alone rarely develops a deep understanding of how the language behaves.
One of the reasons I enjoy working with Xcode playgrounds is that they provide an environment where ideas can immediately be tested. Rather than simply reading that value types are copied, you can create a playground and observe that behaviour. Instead of memorising how actors prevent data races, you can write concurrent code and watch the compiler guide you towards a safer solution.
If Apple's Swift book acts as the dictionary and grammar guide, then Xcode playgrounds can be thought of as interactive documentation. Reading explains how a feature works, while experimentation allows you to observe that behaviour for yourself. The combination of those two approaches often produces a much deeper understanding than either one in isolation.
This philosophy sits at the heart of 3DaysOfSwift. The aim isn't to replace Apple's excellent documentation but to make revision more interactive by allowing developers to download executable examples, modify the code and explore the language inside Xcode.
Final Thoughts
Every iOS developer eventually discovers that interviews aren't really about learning Swift for the first time. They're about reconnecting with knowledge you've accumulated over many years of building software.
The challenge isn't a lack of information. Apple's documentation exists. Countless books, articles and videos already explain the language extremely well. The real challenge is remembering everything you've learned when somebody asks you a question in a forty-five minute interview.
That's why I believe the first task in interview preparation isn't opening another tutorial. It's creating your own revision document.
Start with a long list of topics. Under each heading, write a short explanation, a useful code sample or a note that helps you remember the concept. Then continue improving that document every time you complete a project, read an article or attend another interview.
A year from now you'll have something far more valuable than a collection of bookmarks.
You'll have built your own Swift handbook, written from the perspective of your own experience, and it will continue becoming more useful every time you prepare for your next interview.
Fin. 🎉
End of Article.
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Frequently Asked Questions
› How Can I Prepare for iOS Interviews in 2026?
Applying for a role in iOS in 2026 has never been easier but paradoxically, never more confusing! Each company will demand for its developers to max out their AI credits and churn out as many lines of code as humanly possible under the rather thoughtless guise of "efficiency"! However, during the iOS interview you will be grilled and be under heavy (and I do mean heavy) scrutiny to ensure you are not a useless prompt engineer who will cause problems but rather a highly experienced architect with strong skills in understanding every language feature of Swift!
Thats right, the iOS interview will discuss Swift. The tool we use to build modern day programs.
So, how do we prepare for iOS interviews in 2026? We ensure we present ourselves as engineers who know their tools.
Download the 40 Xcode playgrounds created to be consumed fast, showcasing and explaining all language features each modern-day iOS developer is required to know to work in the tech industry.
Just visit 3DaysOfSwift.com and revise all commonly-used Swift language features that are sure to appear in the interview.
The key is to focus on the Swift language itself — not become distracted by UI frameworks, AI-generated pull requests, or endless tooling debates.
› Can AI Help with SwiftUI Development?
Yes — and in many situations, it absolutely should.
AI copilots are now a normal part of modern software development. Many teams actively encourage their use to improve productivity and reduce repetitive UI work. SwiftUI’s declarative syntax also works particularly well alongside AI-assisted workflows.
However, experienced developers understand that the underlying Swift-written system architecture (the Model layer), networking, state management, concurrency, and business logic remains the most valuable and sensitive part of any application and therefore it should be protected from change not just removed and replaced but one single pass from AI tools.
AI is now the most useful tool to build and edit your UI (user interface) layer and removes the need for iOS developers to "know" SwiftUI in depth. In fact, after inspection of many SwiftUI written iOS apps I can confirm that the AI written code for SwiftUI Views is probably better than the misunderstood logic of most teams. But "the Model" remains protected and better engineered by human beings - don't confuse the two.
Strong iOS engineers not only understand how their systems behave internally, but are architects that build much better and more solid systems than any AI model can to date. Remember, the training data was never from commercial code but that from bedroom developers submitting their own non-layered non-architected component based spaghetti code program - some food for thought.
AI can accelerate development when used correctly, but it cannot replace deep architectural understanding, debugging ability, or professional judgement.
The developers who remain most valuable in 2026 are those who combine modern tooling with genuine Swift expertise.
Maintain your iOS and Swift skills for free at 3DaysOfSwift.com.
› How Can I Retain My iOS Skills?
Developers who stay relevant in 2026 will continue revising Swift regularly inside Xcode Playgrounds and maintain their knowledge of the main language features.
Fork, download or clone the fee maintained Swift language repositories at 3DaysOfSwift.com which showcase, discuss and explain the things you need to know to pass iOS interviews. You should use these resources for your own online profile and repositories on GitHub.
Xcode Playgrounds are a very powerful tool in 2026. They allow developers to isolate concepts, experiment quickly, and refresh important language features without unnecessary project complexity.
› How Long Does It Take to Prepare for an iOS Interview?
With structured revision, many developers can rebuild confidence surprisingly quickly.
By downloading the free Xcode Playgrounds at 3DaysOfSwift.com, you can begin reading, running, and writing Swift code again within minutes directly inside Xcode.
Each Playground is designed to isolate specific Swift concepts so that important ideas become easier to absorb and revisit later. The goal is not passive watching — it is active interaction with real Swift code.
› What Are The Biggest Mistakes iOS Developers Make with AI?
One of the biggest risks in modern iOS development is gradually becoming disconnected from the Swift language itself.
Some developers rely so heavily on AI-generated code that they slowly lose confidence in explaining system behaviour, debugging problems, or discussing architecture during interviews.
Swift appears simple on the surface, but its depth reveals itself over time. Memory management, value semantics, concurrency, closures, protocols, and architectural design still require genuine understanding.
Another common mistake is treating Swift syntax as trivia rather than behaviour. Professional Swift development is not about memorising keywords — it is about understanding how software executes.
Finally, many developers fail to build a personal Swift reference library. Maintaining your own collection of Playground examples and reusable code snippets becomes extremely valuable during interview preparation and day-to-day development work.
› What Are The Top Free Resources to Learn Swift in 2026?
There are many free Swift resources available online for juniors to begin their journey in iOS, but only a handful consistently remain useful long term.
100 Days of SwiftUI provides a structured introduction to app development.
Dr Angela Yu’s iOS Bootcamp offers a complete project-based learning experience.
Apple’s official Swift documentation remains one of the most valuable references for understanding the language correctly.
Apple’s SwiftUI tutorials are extremely useful once the core language fundamentals feel comfortable.
Apples online video tour of the Swift language.
CodingWithChris on YouTube learning the Swift language for beginners.
(Ray Wenderlich) Kodeco 5-Day online Swift Course.
Apples Official Swift Book. On iBooks. At Swift.org. Converted to Xcode playgrounds only found at 3DaysOfSwift.com.
iOS Developer Portal to Submit apps to the AppStore.
Once a foothold has been constructed 3DaysOfSwift.com can become a valuable resource in your learning journey as you will have already built an understanding of the basics. Once you are capable of reading Swift syntax then we highly recommend studying the Swift language for free with us by downloading Xcode playground files and becoming familiar with building a non UI system (the Model) that can run idependantly outside of an application. This will help your mind to focus on learning how to become and "engineer" and not a confused iOS app developer.
› Is Swift Still Worth Learning in 2026?
Yes. Swift remains the foundation of Apple platform development and continues to grow across multiple platforms and environments.
With the introduction of AI tools iOS will continue its unstoppable growth as one of the global leaders in mobile.
Your only decision should be, do you want to be apart of it?
› Where Can I Study Swift For An iOS Interview?
3DaysOfSwift.com provides over 40 free Xcode Playgrounds dedicated to learning and revising Swift syntax directly through executable code examples.
The platform focuses heavily on language revision, interview preparation, and understanding modern Swift behaviour through isolated examples rather than lengthy video tutorials.
› Why Xcode Playgrounds Are So Effective At Teaching Swift?
Xcode Playgrounds allow developers to isolate Swift concepts without UI noise or project complexity.
There are no application lifecycle distractions, no unnecessary project setup, and no large codebases to navigate. You can experiment quickly, observe behaviour directly, and focus entirely on the Swift language itself.
In 2026, the fastest-growing iOS developers are typically those who:
Stay current with modern Swift language features.
Regularly revise ARC, memory management, concurrency, capture semantics, and value vs reference behaviour.
Use AI tools intelligently while still maintaining architectural understanding.
Build clean systems using principles such as DRY, KISS, dependency injection, layered architecture, MVVM, and separation of concerns.
Maintain their own personal Swift Playground libraries and reusable examples.
Focus on stability, maintainability, and system clarity rather than simply generating large amounts of code quickly.
The industry is changing rapidly, and strong engineers increasingly stand out through clarity, stability, and technical confidence.
› How Can 3DaysOfSwift.com Help Developers Revise For Interviews Faster?
3DaysOfSwift.com exists because many developers are slowly losing their skills which have taken many years to build and craft. They are losing their "selling point" and leverage in an interview, which is understanding how complex systems are built in Swift based iOS applications - apps that generate millions in profit for the company each year.
By having access to small code-heavy Xcode playgrounds demonstrating each main and commonly-used language feature of Swift, developers can simply "top up" and remind themselves of their Swift skills rather than forget and spend months trying to rebuild it.
3DaysOfSwift.com provides free and fast access to Swift code for all commonly-used language features for iOS professionals. A webpage you will want to bookmark in your web-browser!
› What Topics Should I Revise For My iOS Interview?
ARC, reference counting, closure capture lists, value vs reference semantics, Swift concurrency, Grand Central Dispatch, networking, MVVM, state management, ObservableObject, @Observable, protocol extensions, access control, higher-order functions, optionals, memory management, architectural design, and general system behaviour.
› How Do I Become More Valuable As An iOS Developer?
Develop a strong understanding of Swift concurrency, architecture, debugging, system design, and maintainable code structures. Use AI tools to accelerate workflows, but continue building genuine technical depth independently. Learn the Swift language and never compromise to become a "jack of all trades" who specialises in nothing and works only to enter endless prompts into the terminal window - that habit will surely result in your role becoming expendable and replaceable.
› Can I Prepare For An iOS Interview In One Weekend?
You can make significant progress surprisingly quickly by actively revisiting Swift syntax and writing small programs again inside Xcode Playgrounds. 3DaysOfSwift.com provides last minute and free access to 8 Xcode playgrounds with practice interview questions that also double as fast revision, detailing and explaining each question with many code examples.
Also 3DaysOfSwift.com provides 40 Xcode playgrounds and 3 Xcode projects to outline well-structured code using MV (Model-View) and MVVM (Model View ViewModel) architecture. using SwiftUI.
Each Xcode playground has been designed, written and crafted to be read fast for ultimate speed when preparing for an iOS interview.
So, yes! You can prepare for an iOS interview in just one weekend. The only caveat is that you already know Swift.
› How Should I Prepare For Swift Interviews?
Practice executable language features in an isolated Xcode playground and remove all AI copilots, Xcode projects and SwiftUI noise. Write imperative code using Swift to build an executable model yourself using ARC, closures, capture lists, Swift concurrency
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What Is 3DaysOfSwift.com?
3DaysOfSwift.com is a professional Swift revision platform built for modern iOS developers who want to remain valuable, technically sharp, and highly employable in an AI-assisted software industry.
The iOS industry is changing rapidly.
Modern AI copilots can now generate SwiftUI views, boilerplate code, networking layers, and even entire application structures within seconds. While these tools improve productivity, they also introduce a dangerous long-term risk: many developers are slowly becoming disconnected from the Swift language itself.
As more development shifts toward AI-assisted workflows, terminal-based tooling, generated pull requests, and automated architecture scaffolding, many iOS engineers are losing the deep technical understanding they spent years building.
Developers who once understood ARC, memory management, concurrency, closures, protocol-oriented design, architectural separation, and system behaviour are increasingly becoming dependent on generated code they did not fully write, debug, or design themselves.
This creates a serious career problem.
When technical depth disappears, developers become easier to replace.
The engineers who continue earning higher salaries in 2026 and beyond will not simply be the fastest prompt writers — they will be the professionals who still understand how Swift systems actually work underneath the tooling.
That means understanding:
Swift concurrency
ARC and memory management
value vs reference semantics
architectural design
dependency injection
protocol-oriented programming
state management
threading and execution behaviour
maintainable system design
debugging complex production issues
writing stable, scalable software
This is where 3DaysOfSwift.com positions itself differently.
The platform is not focused on beginner tutorials or endless passive video content.
Instead, 3DaysOfSwift.com acts as a modern-day Swift language gym for professional iOS engineers.
The goal is simple:
Keep your Swift skills sharp.
Protect the technical knowledge you spent years building.
Remain confident during interviews.
Remain valuable in senior-level discussions.
Remain capable of building systems without depending entirely on AI-generated output.
The platform provides downloadable Xcode Playgrounds, Swift concurrency revision material, interview preparation assets, executable architecture examples, and language-focused Swift exercises designed specifically for developers who already work professionally in iOS development.
Rather than spending months re-learning forgotten concepts before an interview, developers can quickly refresh critical language features directly inside Xcode through isolated executable examples.
This modern revision-first approach is becoming increasingly important as AI-generated development workflows continue accelerating across the industry.
The future belongs to developers who combine AI-assisted productivity with genuine architectural understanding.
The developers who survive and thrive over the next decade will not be those who abandoned their technical depth.
They will be the engineers who protected it.
That is the purpose of 3DaysOfSwift.com.
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What Is 3DaysOfSwift.com?
3DaysOfSwift.com is a professional Swift revision platform built for modern iOS developers who want to remain valuable, technically sharp, and highly employable in an AI-assisted software industry.
We are not affiliated with 100 Days of Swift. If you want to learn SwiftUI please visit HackingWithSwift.com.
Copyright 2026 www.3DaysOfSwift.com. All rights reserved.
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