Books and interactive practice
iOS interview prep
A senior iOS loop rarely fails on syntax. It fails on the second question: the actor that is not isolated the way you said, the view that re-renders because of where you put the state, the cache you sized by count instead of cost.
What the iOS loop scores
| Round | What the interviewer writes down |
|---|---|
| Swift and concurrency | Whether you can explain isolation, Sendable and cancellation from a real bug, not recite the definitions. |
| SwiftUI and UIKit | State ownership, identity and what triggers a body evaluation; when you would still reach for UIKit. |
| Architecture | Module boundaries, dependency direction, and the cost of the pattern you chose on a team of more than three people. |
| Mobile system design | Offline behaviour, sync, caching and lifecycle constraints that a backend design round never asks about. |
| Live coding | Narration, incremental progress and recovery while someone watches your screen. |
Loops differ by company. This is the common shape of senior loops, not a promise about any one employer.
The second question
Follow-ups that decide the round
“You said the view model is @MainActor. What happens to the network call inside it?”
Tests whether you know isolation applies to the function, not the work it awaits.
“The list stutters on an iPhone 11. Where do you look first?”
Tests whether you measure before you change anything, and whether you know what Instruments shows.
“Two teams want to share this module. What changes?”
Tests whether your architecture survives a second owner.
Books for the iOS loop
iOS · $99
The iOS Engineer Playbook
iOS engineers who want the whole career arc in one place
See the book →iOS · $59
The iOS Interview Blueprint
iOS engineers with days or weeks to prepare properly
See the book →iOS · $299
Share Your Screen
iOS engineers who know the material but lose signal in live rounds
See the book →iOS · $89
The 24-Hour iOS Interview Answer Book
iOS engineers with less than a week to prepare
See the book →iOS · From $99
SwiftUI Under Load
Intermediate and senior iOS engineers shipping SwiftUI at scale
See the book →Cross-platform · From $199
Mobile System Design Blueprint
Senior, Staff and Architect candidates facing mobile system design
See the book →Practice
Interview Runtime is the practice layer for iOS: one book and a dashboard that asks the question, scores your answer against a rubric, and asks the follow-up. See Interview Runtime.