TableViewController.swift

////////////////////////////////////////////////////////////////////////////
//
// Copyright 2014 Realm Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////

import UIKit
import RealmSwift

class DemoObject: Object {
    @Persisted var title: String
    @Persisted var date: Date
}

class Cell: UITableViewCell {
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String!) {
        super.init(style: .subtitle, reuseIdentifier: reuseIdentifier)
    }

    required init(coder: NSCoder) {
        fatalError("NSCoding not supported")
    }
}

class TableViewController: UITableViewController {
    let realm = try! Realm()
    let results = try! Realm().objects(DemoObject.self).sorted(byKeyPath: "date")
    var notificationToken: NotificationToken?

    override func viewDidLoad() {
        super.viewDidLoad()

        setupUI()

        // Set results notification block
        self.notificationToken = results.observe { (changes: RealmCollectionChange) in
            switch changes {
            case .initial:
                // Results are now populated and can be accessed without blocking the UI
                self.tableView.reloadData()
            case .update(_, let deletions, let insertions, let modifications):
                // Query results have changed, so apply them to the TableView
                self.tableView.beginUpdates()
                self.tableView.insertRows(at: insertions.map { IndexPath(row: $0, section: 0) }, with: .automatic)
                self.tableView.deleteRows(at: deletions.map { IndexPath(row: $0, section: 0) }, with: .automatic)
                self.tableView.reloadRows(at: modifications.map { IndexPath(row: $0, section: 0) }, with: .automatic)
                self.tableView.endUpdates()
            case .error(let err):
                // An error occurred while opening the Realm file on the background worker thread
                fatalError("\(err)")
            }
        }
    }

    // UI

    func setupUI() {
        tableView.register(Cell.self, forCellReuseIdentifier: "cell")

        self.title = "TableView"
        self.navigationItem.leftBarButtonItem = UIBarButtonItem(title: "BG Add", style: .plain,
                                                                target: self, action: #selector(backgroundAdd))
        self.navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .add,
                                                                 target: self, action: #selector(add))
    }

    // Table view data source

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

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! Cell

        let object = results[indexPath.row]
        cell.textLabel?.text = object.title
        cell.detailTextLabel?.text = object.date.description

        return cell
    }

    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            realm.beginWrite()
            realm.delete(results[indexPath.row])
            try! realm.commitWrite()
        }
    }

    // Actions

    @objc func backgroundAdd() {
        // Import many items in a background thread
        DispatchQueue.global().async {
            // Get new realm and table since we are in a new thread
            autoreleasepool {
                let realm = try! Realm()
                realm.beginWrite()
                for _ in 0..<5 {
                    // Add row via dictionary. Order is ignored.
                    realm.create(DemoObject.self, value: ["title": TableViewController.randomString(), "date": TableViewController.randomDate()])
                }
                try! realm.commitWrite()
            }
        }
    }

    @objc func add() {
        realm.beginWrite()
        realm.create(DemoObject.self, value: [TableViewController.randomString(), TableViewController.randomDate()])
        try! realm.commitWrite()
    }

    // Helpers

    class func randomString() -> String {
        return "Title \(Int.random(in: 0..<100))"
    }

    class func randomDate() -> NSDate {
        return NSDate(timeIntervalSince1970: TimeInterval.random(in: 0..<TimeInterval.greatestFiniteMagnitude))
    }
}