NSBarcelona Realm Demo

FavoritesTableViewController.swift

class FavoritesTableViewController: UITableViewController {

    private var subscription: NotificationToken?
    private var messages: Results<Message>?

    // MARK: - set up the view controller

    override func viewDidLoad() {
        super.viewDidLoad()

        let realm = try! Realm()
        messages = realm.defaultUser.messages.filter("favorite = true")

        subscription = messages?.addNotificationBlock({[weak self] changes  in
            switch changes {
            case .initial:
                self?.tableView.reloadData()
            case .update(_, let deletions, let insertions, let updates):
                self?.tableView.applyChanges(section: 0, deletions: deletions, insertions: insertions, updates: updates)
            default: break
            }
        })
    }

    // MARK: - table view methods

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return messages?.count ?? 0
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let message = messages![indexPath.row]

        let cell = tableView.dequeueReusableCell(withIdentifier: FeedTableViewCell.reuseIdentifier,
                                                 for: indexPath) as! FeedTableViewCell
        cell.configureWithMessage(message)
        return cell
    }

}

Message.swift

class Message: Object {
    
    //MARK: - Properties
    dynamic var id = ""
    dynamic var message = ""
    dynamic var name = ""
    let photos = List<Photo>()
    dynamic var favorite = false
    dynamic var timestamp: TimeInterval = Date().timeIntervalSinceReferenceDate
    
    //MARK: - Meta
    override static func primaryKey() -> String? {
        return "id"
    }
    
    override class func indexedProperties() -> [String] {
        return ["favorite"]
    }
}

Realm+.swift

extension Realm {

    var defaultUser: User {
        return objects(User.self).filter("name = 'me'").first ?? setupDefaultUser()
    }

    func setupDefaultUser() -> User {
        let user = User()
        let createUser = {[unowned self] in
            self.add(user)
            self.add(Photo(value: ["url": "me@2x.png"]))
        }
        if isInWriteTransaction {
            createUser()
        } else {
            try? write(createUser)
        }
        return user
    }
}

UITableView+.swift

import UIKit

private func fromRow(_ section: Int) -> (_ row: Int) -> IndexPath {
    return {row in
        return IndexPath(row: row, section: section)
    }
}

extension UITableView {

    func applyChanges(section: Int, deletions: [Int], insertions: [Int], updates: [Int]) {
        beginUpdates()
        deleteRows(at: deletions.map(fromRow(section)), with: .automatic)
        insertRows(at: insertions.map(fromRow(section)), with: .automatic)
        reloadRows(at: updates.map(fromRow(section)), with: .none)
        endUpdates()
    }
    
}