axiom-cloudkit-ref

CloudKit Reference

Purpose: Comprehensive CloudKit reference for database-based iCloud storage and sync Availability: iOS 10.0+ (basic), iOS 17.0+ (CKSyncEngine), iOS 17.0+ (SwiftData integration) Context: Modern CloudKit sync via CKSyncEngine (WWDC 2023) or SwiftData integration

When to Use This Skill

Use this skill when:

• Implementing structured data sync to iCloud
• Choosing between SwiftData+CloudKit, CKSyncEngine, or raw CloudKit APIs
• Setting up public/private/shared databases
• Implementing conflict resolution
• Debugging CloudKit sync issues
• Monitoring CloudKit performance

NOT for: Simple file sync (use axiom-icloud-drive-ref instead)

Overview

CloudKit is for STRUCTURED DATA sync (records with relationships), not simple file sync.

Three modern approaches:

1. SwiftData + CloudKit (Easiest, iOS 17+)
2. CKSyncEngine (Custom persistence, iOS 17+, WWDC 2023)
3. Raw CloudKit APIs (Maximum control, more complexity)

---

Approach 1: SwiftData + CloudKit (Recommended)

When to use: iOS 17+ apps with SwiftData models

Limitations:

• Private database only (no public/shared)
• Automatic sync (less control)
• SwiftData constraints apply

// ✅ CORRECT: SwiftData with CloudKit sync
import SwiftData

@Model
class Task {
    var title: String
    var isCompleted: Bool
    var dueDate: Date

    init(title: String, isCompleted: Bool = false, dueDate: Date) {
        self.title = title
        self.isCompleted = isCompleted
        self.dueDate = dueDate
    }
}

// Configure CloudKit container
let container = try ModelContainer(
    for: Task.self,
    configurations: ModelConfiguration(
        cloudKitDatabase: .private("iCloud.com.example.app")
    )
)

// That's it! Sync happens automatically

Entitlements required:

• iCloud capability
• CloudKit container

Use axiom-swiftdata skill for SwiftData details

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Approach 2: CKSyncEngine (Modern, WWDC 2023)

When to use: Custom persistence (SQLite, GRDB, JSON) with cloud sync