Coding challenges are one of the most predictable parts of iOS interviews — and also one of the most misunderstood.
Many junior developers assume these challenges exist to test intelligence or trick candidates into failing. In reality, interview coding tasks are designed to observe how you think, how you communicate, and how comfortably you can work with Swift under mild pressure.
At 3DaysOfSwift.com, we’ve seen countless developers struggle not because the problems were hard, but because they had never practised them outside of an interview setting. That’s why we’ve released three FREE coding challenges, delivered as downloadable Xcode projects, designed specifically for interview rehearsal.
These challenges are not puzzles. They are dry runs.
Why Coding Challenges Deserve Dedicated Practice
Interview coding challenges are not about finding the most clever solution. They are about demonstrating:
Clear Swift fundamentals
Logical thinking
Calm problem-solving
The ability to explain decisions out loud
When candidates freeze, rush, or overcomplicate solutions, it’s rarely due to lack of knowledge. It’s because the situation feels unfamiliar.
Practising realistic challenges in advance removes that unfamiliarity. By the time you see a similar problem in an interview, your brain recognises the pattern and responds confidently.
That’s exactly what these challenges are designed to do.
The 3 FREE Coding Challenges
All three challenges are available as part of the FREE iOS Developer Interview Prep Collection and can be downloaded instantly with no signup.
TDD FizzBuzz
FizzBuzz is one of the most common interview problems in software development — not because it’s difficult, but because it reveals how candidates structure logic and communicate intent.
This downloadable Xcode project contains a test-driven Swift solution to the FizzBuzz challenge. It allows you to practise:
Writing clear conditional logic
Structuring simple unit tests
Explaining your reasoning step by step
It’s ideal preparation for interviews that include live coding or take-home exercises.
TDD Palindrome Checker
🔗 Download TDD Palindrome Checker
Palindrome questions appear frequently in iOS interviews because they test attention to detail, edge cases, and string manipulation.
This challenge provides a fully working, test-driven Swift solution that you can study, run, and discuss. It’s particularly useful for practising:
Handling strings safely
Thinking about input validation
Talking through test coverage and assumptions
Once you’ve practised this challenge, similar interview questions feel far less intimidating.
Bug Fix Challenge 🔍🐛
Not all interviews ask you to write code from scratch. Many ask you to fix existing code.
This downloadable Xcode project is a small SwiftUI MVVM app designed to show the date of the next rocket launch. However, the app contains a real bug in unfinished code.
Your task is to:
Understand the existing codebase
Identify the issue
Fix the bug and get the app running correctly
This challenge closely mirrors real-world interview scenarios where candidates are evaluated on debugging skills, reasoning, and composure.
Why These Challenges Work
These challenges are effective because they are:
Realistic
Delivered in Xcode, not pseudocode
Designed to be practised repeatedly
Focused on Swift fundamentals
They help you practise the experience of interview coding, not just the result.
Over time, this builds calmness, confidence, and clarity — all qualities interviewers actively look for.
Part of a Larger FREE Interview Prep Collection
These coding challenges are just one part of the wider FREE iOS Developer Interview Prep Collection available at 3DaysOfSwift.com.
The full collection also includes:
A Swift Xcode playground to read the morning of interviews
Architecture-focused PDFs
Interview readiness guides
Swift question playgrounds for recall practice
Everything is free, downloadable, and designed to be reused throughout your career.
Download Them Now. Practise Before It Matters.
If you have an iOS interview coming up in 2026 — or any time after — these three coding challenges are some of the best preparation you can do.
No signup. No paywall. No pressure.
👉 Download the 3 FREE Coding Challenges Practise calmly. Explain confidently. And walk into your next interview prepared.
One challenge at a time can change your career. 🚀
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Swift Online Course
Also, as an additional bit of help 3DaysOfSwift has a free online 3-day course written by a successful iOS Developer with almost two decades experience in iOS.
3 Day Online Swift Course (written by senior iOS Developers)
Learn Swift and enrol in our 3-day online course. We have 3 days of instructional videos pair programming with our experienced instructor and Senior iOS Developer who guides you through writing code for each main language feature of Swift. There is extra coding practice too (with no videos so it's faster).
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Swift Study Guide
Also, as an additional bit of help 3DaysOfSwift has the Swift Study Guide (listed below and to download), which is a list of Swift language features each iOS Developer should know before applying for jobs in the tech industry.
List of Swift Language Features
Download the list of topics (Swift language features) you will be required to know in order to pass an interview for an iOS Developer role.
Download
Beginner Topics
Topic 1: The Basics & Foundational Types
Topic 2: Control Flow
Topic 3: Optionals
Topic 5: Classes
Topic 6: Structs
Topic 7: Enums
Topic 8: Value Types & Reference Types
Topic 9: ARC (Automatic Reference Counting)
Mid-level Topics
Topic 10: Extensions
Topic 11: Protocols
Topic 12: Concurrency
Topic 13: Error Handling
Topic 14: Generics
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Swift Career Tips 🚀
Also, as an additional bit of help 3DaysOfSwift has outlined a few career tips that might help as you start your journey as an iOS Developer applying for jobs writing software for Apple devices.
Tips 🚀
Below we have included a few career tips to help get you started as a Junior iOS Developer working in the tech industry.
Focus on learning the Swift language itself. Most team members start their learning journey by studying Xcode and building apps. It's a lot of information and plenty to get confused about. Most of your colleagues will have many gaps in knowledge that affect their every-day anxiety with completing tasks and having it reviewed by others. Instead, why not become the one of the reviewers? Our advice is to stand out in the tech industry and if you want to stand out I would suggest becoming very knowledgable about the language itself; Every single developer will be using it and they will all be competing over Architecture and not the best use of language features. Armed with an incredible understanding of the language you will have the confidence in knowing you can maintain any existing product on the market.
Gather "Career Things" like they were collectibles in a game. This easy-to-remember and rather broad term is a great bit of advice. Too many engineers let the months go by without really taking on board many exciting projects or doing anything that wows any one. This is a terrible idea in every way. Stand out. Be the best at something (like understanding the language). When you change positions and apply to a different company you will have an interview and they'll grill you with many questions. The main bits to know are these; Your CV gets you the interview. You display your worth in the interview.
Your CV gets you the interview: Your short 2 page bullet-pointed CV is simply a list of amazing things you did to improve the team, the social element, the code quality, the income, how you increased user retention, how you added a successful feature and improved the app. You must collect career things.
You display worth in the interview: In the interview you want to fill the hour with saying similar phrases non-stop to "I was able to tweak the values and affect the income of the product simply by reducing the friction of the onboarding and providing a more seamless and pleasant user experience for the user. We now have only a 14% drop compared to most companies that have around 30% typically." Notice how you use "we" when referring to your current company in interviews. To simplify the phrase just-used, "I helped my company move forward. I improved the product, which led to an increased user experience and ultimately more profits for the company. I am a team player and I will improve your company at every opportunity possible."
Become confident in Interviews. You are now a talented Swift engineer who understands the Swift language and has a list of successful results you can pull out of the bag and discuss and any interview. You are constantly and infinitely talking about specifics of the Swift language and how cool and useful it is. You are stacking up one example after another of how you affected the results of the team and the company. You are great at telling these stories. The world is your oyster and you can be confident in your abilities as well as your choices in life.
Move company every 2 years. Ask for a £10,000 increase. When you become bored at your current job because you know too much think about moving, upgrading your job title and doubling your annual salary.
Be driven and be proud that you help keep the world moving by maintaining the digital services we all love and are constantly glued to.
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