Agent-skills-standard ios-persistence

Implement local persistence with SwiftData, Core Data, and Keychain. Use when setting up SwiftData models, Core Data stacks, or local persistence in iOS. (triggers: **/*.xcdatamodeld, **/*Model.swift, PersistentContainer, FetchRequest, ManagedObject, Query, ModelContainer, Repository)

install

source · Clone the upstream repo

git clone https://github.com/HoangNguyen0403/agent-skills-standard

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/HoangNguyen0403/agent-skills-standard "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/ios/ios-persistence" ~/.claude/skills/hoangnguyen0403-agent-skills-standard-ios-persistence && rm -rf "$T"

manifest: skills/ios/ios-persistence/SKILL.md

source content

iOS Persistence

Priority: P0

Implementation Workflow

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

See SwiftData and Core Data implementation examples

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