swift-anti-pattern-guard

Swift Anti-Pattern Guard

Detect and replace the highest-impact forbidden patterns. Advisory unless hooks already block them.

Non-negotiables

ALWAYS	NEVER
Report file + pattern + replacement	Auto-rewrite entire modules without review
Align with repository guidance and deployment targets	Treat “legacy file” as a permanent exemption without explanation

Patterns (phase 1)

1. Observation family

Forbidden: ObservableObject, @Published, @StateObject, @ObservedObject, @EnvironmentObject Replace: @Observable + plain properties; own with @State / inject via @Environment

2. GCD main queue

Forbidden: DispatchQueue.main.async, asyncAfter Replace: @MainActor, await MainActor.run, Task { @MainActor in }

3. NavigationView

Forbidden: NavigationView Replace: NavigationStack or NavigationSplitView

4. Core Data

Forbidden: NSManagedObject, @FetchRequest, NSPersistentContainer Replace: SwiftData @Model, @Query, ModelContext

How to run

1. Grep the path for forbidden tokens.
2. Group findings by file.
3. For each: why it hurts (concurrency, invalidation, maintenance) + modern replacement.
4. Suggest a minimal fix when local; do not drive-by refactor unrelated code.

rg -n "ObservableObject|@Published|@StateObject|@ObservedObject|DispatchQueue\\.main|NavigationView|NSManagedObject|@FetchRequest" --glob '*.swift' .

Rationalizations

Excuse	Reality
"Only one ObservableObject"	In greenfield Observation code, consistency avoids two state models
"DispatchQueue is clearer"	@MainActor is clearer under Swift 6
"Core Data already works"	New code is SwiftData; migrate when touching area

Pre-finish checklist

• Grep run on target path
• Findings include replacement
• No silent ignore of matches without reason