Interview guides / ios

God settings controller: iOS Interview Question

God settings controller interview question with a clear example answer for iOS engineers. Practice with AceMobileInterview.

This is a common iOS interview topic: God settings controller.

Below is a concise answer you can adapt in a real interview, then go deeper in the full AceMobileInterview track.

1. 1.SettingsViewController does networking, parsing, disk I/O, and UI—and embeds an API key. Refactor the worst smells (≈45–60 min).

   ## Scenario Classic “temporary” VC that absorbed every concern. ## How to investigate - Skim `SettingsViewController.swift` size and responsibilities - Grep for `api_key` / `sk_live` / secrets - Note `Data.write` on the button action (main thread) ## Planted bug 1: Hardcoded API key **Symptom:** Secret in source control **Root cause:** `let apiKey = "sk_live_..."` in the VC **Fix:** Move to xcconfig / info plist placeholder / env; never commit real keys; use a stub in the exercise ## Planted bug 2: God object **Symptom:** Untestable blob **Root cause:** URLSession + JSONDecoder + UserDefaults + UI in one type **Fix:** Extract `SettingsRepository` (load/save remote+local); VC becomes binder ## Planted bug 3: Main-thread disk write **Symptom:** Brief hitch on Save **Root cause:** Synchronous `data.write(to:)` on main **Fix:** Background write; atomic replace; main-thread success toast only ## Optimization tips - Interview bar is “extract boundaries,” not a perfect architecture diagram - Call out how you’d add unit tests around the repository ## What to say in the interview - How you prioritized secret removal first - What you left as intentional stretch