IOS Developer Competency Matrix

iOS Developer Competency Matrix

Use this skill as a review + implementation checklist when building features in this repo.

1) Quick triage questions (pick the right lane)

Answer these before coding:

• Is this mostly UI (SwiftUI/UIKit), domain logic, data/network, or platform integration?
• Do we need async work? If yes: can we use structured concurrency end-to-end?
• What are the states (loading/empty/error/success) and how are they represented?
• What must be testable (unit/UI/snapshot) and what is the acceptance criteria?

2) Swift language & concurrency rules

• Prefer Swift concurrency (async/await) over nested completion handlers.
• UI mutations on the main actor (@MainActor / await MainActor.run).
• Use actors or isolated types for shared mutable state.
• Watch for ARC traps: closures capturing self → use [weak self] when needed.

3) UI (SwiftUI + UIKit)

• SwiftUI: choose the right state tool (@State, @Binding, @StateObject, @ObservedObject, @Environment).
• UIKit: respect lifecycle, safe areas, and Auto Layout anchors.
• Interop:
  • SwiftUI in UIKit: UIHostingController
  • UIKit in SwiftUI: UIViewRepresentable / UIViewControllerRepresentable

4) Architecture & patterns

Default opinionated picks (override only with reason):

• SwiftUI screens: MVVM (View + ViewModel + injected services)
• Navigation complexity: add a Coordinator (or a routing layer)
• Scale/enterprise modules: consider Clean boundaries (domain/use-cases, repositories)
• Dependency injection: start with initializer injection; add a container only when it pays off.

5) Networking & data

• Prefer URLSession + Codable with explicit domain errors.
• Model API errors → map to user-facing messages at the edge.
• Persistence: SwiftData/Core Data for relational graphs; Keychain for secrets; UserDefaults for prefs.

6) Platform integration

• Understand scene lifecycle vs app delegate responsibilities.
• For background work, pick the correct API (and keep expectations realistic).
• Device features (camera/location/push/biometrics): treat permission flows + failure paths as first-class.

7) Quality: tests, debugging, performance

• Unit tests for logic; UI tests for key flows; snapshot tests for UI regressions (if used here).
• Use Instruments for leaks/time/energy when performance matters.

8) Release readiness

• HIG alignment + accessibility basics.
• Review Guideline landmines: privacy disclosures, permissions strings, incomplete flows.
• CI/CD: prefer SPM; automate build/test; keep signing/provisioning sane.

References

• Deep checklists + snippets: references/checklists.md

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