### Start and Manage Sync Engine (Swift)

Source: https://github.com/orloff-n/takeoffkit/blob/main/README.md

Initiates the TKSyncEngine to perform CloudKit operations. Allows for sending local changes and fetching remote changes. Operations are queued and executed when the engine is running.

```swift
engine.start() // Start syncing

// Send changes
engine.sendChanges(modify: modifiedItems, delete: deletedIDs)

// Fetch changes
engine.fetchChanges(token: lastChangeToken)
```

--------------------------------

### Implement TakeoffKit Sync Engine Delegate Methods

Source: https://github.com/orloff-n/takeoffkit/blob/main/README.md

This example outlines the implementation of various `TKSyncEngineDelegate` methods in Swift, covering error handling, account status changes, token updates, fetching modifications and deletions, conflict resolution, and handling send/fetch failures.

```swift
extension YourDelegate: TKSyncEngineDelegate {
    func syncEngine(_ engine: TKSyncEngine, didStopWithError error: any Error) {
        // Handle errors
    }
    
    func syncEngine(_ engine: TKSyncEngine, didChangeAccountStatus accountStatus: CKAccountStatus) {
        // React to account status changes
    }
    
    func syncEngine(_ engine: TKSyncEngine, didUpdateChangeToken changeToken: CKServerChangeToken?) {
        // Persist the received token
    }
    
    func syncEngine(_ engine: TKSyncEngine, didFetchModifications modifications: [TKRecord]) {
        // Persist changes
    }
    
    func syncEngine(_ engine: TKSyncEngine, didFetchDeletions deletions: [(recordID: String, recordType: String)]) {
        // Persist changes
    }
    
    func syncEngine(_ engine: TKSyncEngine, fetchDidFailFor failedIDs: [String : any Error]) {
        // Handle per-record errors
    }
    
    func syncEngine(_ engine: TKSyncEngine, didSendModifications modifiedRecords: [TKRecord]) {
        // Update local items (e.g. mark them as synced)
    }
    
    func syncEngine(_ engine: TKSyncEngine, didSendDeletions deletedIDs: [String]) {
        // Update local items (e.g. hard delete them)
    }
    
    func syncEngine(_ engine: TKSyncEngine, sendDidFailFor failedIDs: [String : any Error]) {
        // Handle per-record errors
    }
    
    func syncEngine(_ engine: TKSyncEngine, shouldResolveConflict conflict: TKConflict) -> CKRecord {
        // Implement your conflict resolution logic. Example:
        if let clientDate = conflict.clientRecord.modificationDate,
           let serverDate = conflict.serverRecord.modificationDate {
            return clientDate > serverDate ? conflict.clientRecord : conflict.serverRecord
        }
        
        return conflict.clientRecord
    }
}

// Assign the sync engine's delegate:
engine.delegate = self
```

--------------------------------

### Prepare Data Models for CloudKit Sync (Realm Example)

Source: https://github.com/orloff-n/takeoffkit/blob/main/README.md

This code snippet demonstrates how to make a Realm model conform to the `TKSyncable` protocol, which is required for data synchronization with CloudKit using TakeoffKit. It includes the necessary properties like `tkMetadata`, `tkRecordID`, and `tkProperties`.

```swift
final class Folder: TKSyncable {
    @Persisted(primaryKey: true) var id: ObjectId
    @Persisted var index: Int
    @Persisted var name: String
    @Persisted(originProperty: "folder") var accounts: LinkingObjects<Account>


    // TKSyncable conformance:
    @Persisted var tkMetadata: Data?
    var tkRecordID: String { id.stringValue }
    var tkProperties: [String: TKSyncableValue] {
        [
            "index": .value(index),
            "name": .encryptedValue(name)
        ]
    }
}
```

--------------------------------

### Initialize TakeoffKit Sync Engine

Source: https://github.com/orloff-n/takeoffkit/blob/main/README.md

This Swift code shows how to create a `TKSyncEngineConfiguration` with essential CloudKit details like container ID, zone name, and subscription ID, and then use this configuration to initialize the `TKSyncEngine`.

```swift
let config = TKSyncEngineConfiguration(
    containerID: "iCloud.com.example.MyApp",
    zoneName: "MyDataZone",
    subscriptionID: "MySubscription"
)

let engine = TKSyncEngine(configuration: config)
```

--------------------------------

### Handle Remote Notifications (Swift)

Source: https://github.com/orloff-n/takeoffkit/blob/main/README.md

Registers the application for remote notifications and defines how to handle incoming CloudKit notifications. Filters notifications by subscription ID and processes them for real-time updates.

```swift
final class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        application.registerForRemoteNotifications()
        return true
    }
    
    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any]) async -> UIBackgroundFetchResult {
        // Filter CloudKit notifications by subscriptionID (should match TKSyncEngineConfiguration)
        if let notification = CKNotification(fromRemoteNotificationDictionary: userInfo),
           notification.subscriptionID == "MySubscription" {
            // Fetch changes and return the appropriate UIBackgroundFetchResult
        }
        
        // Other notifications
        return .noData
    }
}
```

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