Realm Sync Service: Detecting changes

Uploadable+changes.swift

typealias Syncable = Object & Uploadable 

struct Update {
    let insertions: [Syncable]
    let modifications: [Syncable]
    let deletedIds: [String]
    let type: Syncable.Type
}

extension Uploadable where Self: Object {

    ...

    static func registerNotificationObserver(for realm: Realm, callback: @escaping (Update) -> Void) -> NotificationToken {
        let objects = realm.objects(self)
        var objectIds: [String]!

        return objects.observe { changes in
            switch changes {
            case .initial(_):
                objectIds = objects.map { $0.getId() }
            case .update(let collection, let deletions, let insertions, let modifications):
                let insertedObjects = insertions.map { collection[$0] }
                let modifiedObjects = modifications.map { collection[$0] }
                let deletedIds = deletions.map { objectIds[$0] }

                let update = Update(insertions: insertedObjects, modifications: modifiedObjects, deletedIds: deletedIds, type: Self.self)
                callback(update)

                objectIds = objects.map { $0.getId() }
            case .error(_):
                break
            }
        }
    }

}