ios-persistence

Included with Lifetime

$97 forever

Implement local persistence with SwiftData, Core Data, and Keychain. Use when setting up SwiftData models, Core Data stacks, or local persistence in iOS.

General

What this skill does

# iOS Persistence

## **Priority: P0**

## Implementation Workflow

1. **Choose storage tier** — SwiftData for iOS 17+, Core Data for legacy, Keychain for secrets, UserDefaults for flags only.
2. **Define models** — Use `@Model` macro (SwiftData) or `.xcdatamodeld` (Core Data).
3. **Configure container** — Use `@MainActor` for `ModelContainer` (SwiftData) or `NSPersistentContainer` (Core Data).
4. **Perform background writes** — Use `newBackgroundContext()` (Core Data) to avoid UI lag; never heavy I/O on `viewContext`.
5. **Secure sensitive data** — Use Keychain for tokens and PII; never store in `UserDefaults`.

See [SwiftData and Core Data implementation examples](references/implementation.md)

## Anti-Patterns

- **No Heavy I/O on `viewContext`**: Use private background contexts
- **No String-based Predicates**: Use KeyPaths or generated helpers
- **No Missing Merge Strategy**: Set `mergePolicy` explicitly (e.g., `mergeByPropertyObjectTrump`)

## References

- [SwiftData & Core Data Implementation](references/implementation.md)

Files: 3

Size: 5.2 KB

Complexity: 24/100

Category: General

Source: https://github.com/hoangnguyen0403/agent-skills-standard/tree/main/skills/ios/ios-persistence

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