axiom-realm-migration-ref

Realm to SwiftData Migration — Reference Guide

Purpose: Complete migration path from Realm to SwiftData Swift Version: Swift 5.9+ (Swift 6 with strict concurrency recommended) iOS Version: iOS 17+ (iOS 26+ recommended) Context: Realm Device Sync sunset Sept 30, 2025. This guide is essential for Realm users migrating before deadline.

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Critical Timeline

Realm Device Sync DEPRECATION DEADLINE = September 30, 2025

If your app uses Realm Sync:

• ⚠️ You MUST migrate by September 30, 2025
• ✅ SwiftData is the recommended replacement
• ⏰ Time remaining: Depends on current date, but migrations take 2-8 weeks for production apps

This guide provides everything needed for successful migration.

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Migration Strategy Overview

Phase 1 (Week 1-2): Preparation & Planning
├─ Audit current Realm usage
├─ Understand model relationships
├─ Plan data migration path
└─ Set up test environment

Phase 2 (Week 2-3): Development
├─ Create SwiftData models from Realm schemas
├─ Implement data migration logic
├─ Convert threading model to async/await
└─ Test with real data

Phase 3 (Week 3-4): Migration
├─ Migrate existing app users' data
├─ Run in parallel (Realm + SwiftData)
├─ Verify CloudKit sync works
└─ Monitor for issues

Phase 4 (Week 4+): Production
├─ Deploy update with parallel persistence
├─ Gradual cutover from Realm to SwiftData
├─ Deprecate Realm code
└─ Monitor CloudKit sync health

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Part 1: Pattern Equivalents

Model Definition Conversion

Realm → SwiftData: Basic Model

// REALM
class RealmTrack: Object {
    @Persisted(primaryKey: true) var id: String
    @Persisted var title: String
    @Persisted var artist: String
    @Persisted var duration: TimeInterval
    @Persisted var genre: String?
}

// SWIFTDATA
@Model
final class Track {
    @Attribute(.unique) var id: String
    var title: String
    var artist: String
    var duration: TimeInterval
    var genre: String?

    init(id: String, title: String, artist: String, duration: TimeInterval, genre: String? = nil) {
        self.id = id
        self.title = title
        self.artist = artist
        self.duration = duration
        self.genre = genre
    }
}