如何将Realm通知抽象为带有闭包的通用结构？

Question

My view model currently contains the following code:

private let project = RLMProject()
var projectToken: NotificationToken? = nil

projectToken = project.getDatabase()?.objects(RLMProject.self).observe { changes in ...

With support in:

final class RLMProject: Object, Decodable, DatabaseLayer { ... 
    typealias T = RLMProject
}

protocol DatabaseLayer {
    associatedtype T: Object

    func getDatabase() -> Realm?
}

extension DatabaseLayer {
    func getDatabase() -> Realm? {
        do {
            return try Realm(fileURL: userRealmFile)
        } catch let error {
            DDLogError("Database error: \(error)")
            return nil
        }
    }
...

I want to make the getDatabase() function private but am having trouble encapsulating the notification closure where the view model can still set it for any <T: Object> , without having to know the internals of anything about Realm.

Something from this:

projectToken = project.getDatabase()?.objects(RLMProject.self).observe { [unowned self] ...

to this:

projectToken = project.setupNotificationToken { changes in ...

Answer 1

Seems I got it working.

// Setup to observe Realm `CollectionChange` notifications
func setupNotificationToken(for observer: AnyObject, _ block: @escaping () -> Void) -> NotificationToken? {
    if let database = self.getDatabase() {
        return database.objects(T.self).observe { [weak observer] (changes: RealmCollectionChange) in
            if observer != nil {
                DDLogDebug("NotificationToken triggered on: \(observer!) for object: \(T.self)")
            }
            block()
        }
    } else {
        return nil
    }
}

Example:

projectToken = project.setupNotificationToken(for: self) { [unowned self] in
    self.updateVC()
    }