Prepare for iOS interviews with ease
The iOS interview prep platform with Swift coding questions you can run, clear answers, mobile system design and a roadmap. All in simple English.
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Longest Substring Without Repeating Characters
Given a string s, return the length of the longest part of it that has no repeated characters.
lengthOfLongestSubstring("bbbbb") // 1
Use a sliding window. Try to solve it in one pass.
func lengthOfLongestSubstring(_ s: String) -> Int {
var lastSeen: [Character: Int] = [:]
var start = 0
var best = 0
for (index, char) in s.enumerated() {
if let seen = lastSeen[char], seen >= start {
start = seen + 1
}
lastSeen[char] = index
best = max(best, index - start + 1)
}
return best
}133
practice questions
33
Swift questions with tests
8
system design walkthroughs
24
guide chapters
88
roadmap topics
Everything in one place
All you need to get the iOS job
Stop jumping between blog posts and old videos. Practise, learn and plan in one place.
Swift that really runs
Write Swift in a real editor. Run it with the Swift 6.4 compiler and see which tests pass.
Clear quiz answers
ARC, actors, SwiftUI state, the layout cycle and more. A TL;DR first, then examples.
Mobile system design
Design an image cache, a chat app or an offline-first notes app, step by step.
UI coding
Build real SwiftUI and UIKit screens, then compare with a full solution.
A roadmap that links to practice
88 topics in learning order. Each one links to the questions that test it.
Study plans
iOS 75, plus 1 week, 1 month and 3 month plans. Know exactly what to do each day.
Interview guides
How the rounds work, your resume, behavioral answers and how to negotiate.
Track your progress
Completed questions, submissions, a streak and a dashboard that shows what is left.
Practice questions
Every kind of iOS interview question
Coding rounds, knowledge rounds, system design and take-home UI tasks. Practise each one the way it is asked.
Swift coding
33 questionsQuiz
84 questions- What is the difference between a struct and a class?Easy
- What are value semantics, and how does copy-on-write work?Medium
- What are optionals in Swift, and how do you unwrap them safely?Easy
- What is protocol-oriented programming in Swift?Medium
Study plans
A plan for the time you have
Interview next week? Or in three months? Follow a plan and know exactly what to do each day.
Roadmap
Know what to learn next
The roadmap puts every iOS interview topic in a simple order, from Swift basics to system design. Each topic tells you what to explain and links to practice.
- 1Swift fundamentals7 topics
- 2Protocols and generics5 topics
- 3Memory management5 topics
- 4Concurrency7 topics
- 5UIKit5 topics
- 6SwiftUI5 topics
- 7Architecture5 topics
- …and 9 more sections
A Swift playground in your browser
Test an idea, check how a closure captures a value, or try async/await. No Xcode needed.
FAQ
Questions people ask
Is iosNudge free?+
Yes. Every question, answer, guide and study plan is free. You only need to sign in to run code and save your progress.
Does my Swift code really run?+
Yes. When you click Run, we compile your code with the real Swift 6.4 compiler on Linux and run it against tests. You see which tests pass, what your code printed, and any compiler errors with line numbers.
Can I run SwiftUI or UIKit code here?+
No. The browser runner is Linux Swift, so it has Foundation but no Apple UI frameworks. For UI questions you build the screen in Xcode, then compare it with our complete solution.
I am short on time. Where do I start?+
Start with iOS 75: the 75 most important questions across Swift, concurrency, UIKit, SwiftUI, architecture and system design. If your interview is in a few days, use the 1 week plan.
Is the English easy to follow?+
Yes. Every answer uses short sentences and simple words, starts with a TL;DR, and shows a code example for each idea.
Your next iOS job starts here
Start with one question today. Small steps every day add up.
Start practising