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name: ios-data description: Master iOS data persistence - SwiftData, Core Data, Keychain, CloudKit sasmp_version: "1.3.0" version: "2.0.0" bonded_agent: 04-data-persistence bond_type: PRIMARY_BOND last_updated: "2024-12"

iOS Data Persistence Skill

Store, sync, and secure data in iOS applications

Learning Objectives

By completing this skill, you will:

• Implement data persistence with SwiftData (iOS 17+)
• Master Core Data for complex data models
• Secure sensitive data with Keychain
• Sync data across devices with CloudKit

Prerequisites

Requirement	Level
iOS Fundamentals	Completed
Swift	Intermediate

Storage Decision Matrix

Storage Type	Use Case	Encrypted	Synced
UserDefaults	Settings	No	Optional
File System	Documents	Optional	Optional
Keychain	Secrets	Yes	Optional
SwiftData	Structured data	No	Optional
Core Data	Complex models	No	Optional
CloudKit	Cross-device	Yes	Yes

Curriculum

Module 1: UserDefaults & AppStorage (2 hours)

Topics:

• UserDefaults basics
• @AppStorage in SwiftUI
• App Groups for sharing

Module 2: SwiftData (iOS 17+) (6 hours)

Topics:

• @Model macro
• ModelContext and @Query
• Relationships and migrations

Module 3: Core Data (6 hours)

Topics:

• NSManagedObject
• NSFetchRequest
• Background contexts
• Migrations

Module 4: Keychain (4 hours)

Topics:

• Keychain Services API
• Biometric access control
• Secure wrapper implementation

Module 5: CloudKit (5 hours)

Topics:

• CKContainer and databases
• CKRecord operations
• Sync strategies

Assessment Criteria

Criteria	Weight
Storage selection	20%
SwiftData/Core Data	30%
Keychain security	25%
CloudKit sync	25%

Skill Validation

1. Settings Manager: UserDefaults with AppStorage
2. Task App: SwiftData with relationships
3. Secure Vault: Keychain with biometrics
4. Syncing Notes: CloudKit integration