@IBAction func buttonPressed(_ sender: Any) {
  performSegue(withIdentifier: "GoToSecondScreen", sender: self)
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  if segue.identifier == "GoToSecondScreen" {
    // We are not allowed to create a ViewController Object regularly, like
    // let destinationVC = SecondViewController()
    // Instead, we do
    let destinationVC = segue.destination as! SecondViewController
    destinationVC.textPassedOver = textField.text
  }
}

protocol ChangeCityDelegate{
    func userEnteredANewCityName(name: String)
}

var delegate: ChangeCityDelegate?

if (delegate != nil) {
  delegate?.userEnteredANewCityName(name: city)
  // close this ViewController
  self.dismiss(animated: true, completion: nil)
}

import UIKit

class CustomMessageCell: UITableViewCell {
    @IBOutlet var messageBackground: UIView!
    @IBOutlet var avatarImageView: UIImageView!
    @IBOutlet var messageBody: UILabel!
    @IBOutlet var senderUsername: UILabel!

    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code goes here
    }
}

class ChatViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
  @IBOutlet var messageTableView: UITableView!

  override func viewDidLoad() {
    super.viewDidLoad()

    //TODO: Set yourself as the delegate and datasource here:
    messageTableView.delegate = self
    messageTableView.dataSource = self

    //TODO: Register your MessageCell.xib file here:
    messageTableView.register(UINib(nibName: "MessageCell", bundle: nil), forCellReuseIdentifier: "customMessageCell")
  }

  //TODO: Declare cellForRowAtIndexPath here:
  // This message gets called for every single cell that exists inside the tableView
  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
      let cell = tableView.dequeueReusableCell(withIdentifier: "customMessageCell", for: indexPath) as! CustomMessageCell
      let messageArray = ["First message", "Second message", "Third message"]
      cell.messageBody.text = messageArray[indexPath.row]
      return cell
  }


  //TODO: Declare numberOfRowsInSection here:
  // Specify how many cells you want and what cells you want to display
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
      return 3
  }
}

override func viewDidLoad() {
  super.viewDidLoad()

  //TODO: Set yourself as the delegate and datasource here:
  messageTableView.delegate = self
  messageTableView.dataSource = self

  //TODO: Register your MessageCell.xib file here:
  messageTableView.register(UINib(nibName: "MessageCell", bundle: nil), forCellReuseIdentifier: "customMessageCell")
  configureTableView()
}

//TODO: Declare configureTableView here:
func configureTableView() {
  messageTableView.rowHeight = UITableView.automaticDimension
  messageTableView.estimatedRowHeight = 120.0
}

extension TodoListViewController: UISearchBarDelegate {

    // This method will be triggered as "Enter" is typed
//    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
//      queryData(text: searchBar.text!)
//    }

    // This method will be triggered as users are typing
    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
      // Do something as users clear the Search Bar
      if searchBar.text?.count == 0 {
        reloadData()
      } else {
        // Query data as users are typing to improve user experience.
        queryData(text: searchBar.text!)
      }
    }
}

class ItemViewController: UIViewController {

  var searchController : UISearchController!

  override func viewDidLoad() {
    super.viewDidLoad()

    // Set searchBar inside NavigationController
    initUISearchController()
  }
}

extension ItemViewController: UISearchControllerDelegate, UISearchBarDelegate {

    // This method will be triggered as "Enter" is typed
    //    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
    //        updateTableView(text: searchBar.text!)
    //    }

    func initUISearchController() {
        searchController = UISearchController(searchResultsController: nil)
        searchController.delegate = self
        searchController.searchBar.delegate = self
        searchController.hidesNavigationBarDuringPresentation = true
        searchController.dimsBackgroundDuringPresentation = true

        navigationItem.searchController = searchController
        definesPresentationContext = true
    }

    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
        // Reload all the data as users clear the Search Bar
        if searchBar.text?.count == 0 {
            loadItems()
            DispatchQueue.main.async {
                // No longer have the cursor and also the keyboard should go away
                searchBar.resignFirstResponder()
            }
        } else {
            // Query data as users are typing to improve user experience.
        }
    }
}

//MARK: - Networking
func retrieveMessage() {
//TODO: Retrieve messages from Firebase

}


//MARK: - JSON Parsing

class TodoListViewController: UISearchBarDelegate {
  func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
    <#code#>
  }
}

class TodoListViewController {

}

//MARK: - SearchBar methods
extension TodoListViewController: UISearchBarDelegate {
  func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
    <#code#>
  }
}

func fetchRequest(request: NSFetchRequest<MyTodoeyItem>) {
  do {
    itemArray = try context.fetch(request)
    } catch {
      print("Error fetching data from context \(error)")
    }
  }

fetchRequest(with: request)

class A {
  let b = B()
  b.data = "xxx"
}

let locationManager = CLLocationManager()
override func viewDidLoad() {
  super.viewDidLoad()

  locationManager.delegate = self
  locationManager.requestWhenInUseAuthorization();
}

// Asynchronous method (It works in the background), call didUpdateLocations and didFailWithError methods to handle callbacks
locationManager.startUpdatingLocation()

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
  // the laster the more accurate
  let location = locations[locations.count - 1]
  // Accuracy means the spread of possible locations.
  // When that value is negative, that represents an invalid result
  if (location.horizontalAccuracy > 0) {
    // Unless you want to destroy users' battery, you should stop updating locations as soon as you get the valid data
    locationManager.stopUpdatingLocation()
    print("(\(location.coordinate.longitude), \(location.coordinate.latitude))")
  }
}

func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
  // Location unavailable
  print(error)
}

class DataManager {
    func save(key: String, value: String, callback: (Bool, String) -> Void){
      // Do something time consuming
        let isSuccess = true
        let message = "\(key) saved"
        callback(isSuccess, message)
    }
}

class MyViewController: UIViewController {

  func completion(isSuccess: Bool, message: String) {
    print("isSuccess:\(isSuccess), message:\(message)")
  }

  @IBAction func registerPressed(_ sender: AnyObject) {
    let dataManager = DataManager()
    dataManager.save(key: "name", value: "Nick", callback: completion)
  }
}

let dataManager = DataManager()
dataManager.save(key: "name", value: "Nick") { (isSuccess, message) in
  print("isSuccess:\(isSuccess), message:\(message)")
}

DispatchQueue.global(qos: .background).async {
  //do something
}

DispatchQueue.main.async {
  //do something
}

let defaults = UserDefaults.standard
defaults.set(0.24, forKey: "volumn")
defaults.set(true, forKey: "musicOn")
defaults.set("Alex", forKey: "playerName")
defaults.set(["musket", "helmet"], forKey: "weapons")
defaults.set(["id": "A001", "title": "kill Demogorgon"], forKey: "mission")
defaults.set(Date(), forKey: "appLastOpenedByUser")

if let volumn = defaults.float(forKey: "volumn") as? Float {
  print("volumn:\(volumn)")
}
if let musicOn = defaults.bool(forKey: "musicOn") as? Bool {
  print("musicOn:\(musicOn)")
}
if let playerName = defaults.string(forKey: "playerName") {
  print("playerName:\(playerName)")
}
if let appLastOpenedByUser = defaults.object(forKey: "appLastOpenedByUser") {
  print("appLastOpenedByUser:\(appLastOpenedByUser)")
}
if let weapons = defaults.array(forKey: "weapons") as? [String] {
  print("weapons:\(weapons)")
}
if let mission = defaults.dictionary(forKey: "mission") as? Dictionary<String, String> {
  print("mission:\(mission)")
}

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    print(NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).last! as String)
    return true
}

let dataFilePath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first?.appendingPathComponent("Items.plist")

import Foundation

class TodoeyItem: Encodable {
    var title: String
    var done: Bool

    init(title: String, done: Bool) {
        self.title = title
        self.done = done
    }
}

do {
  let encoder = PropertyListEncoder()
  let data = try encoder.encode(self.itemArray)
  try data.write(to: dataFilePath!)
  } catch {
    print("Error encoding item array")
  }

import Foundation

class TodoeyItem: Codable {
    var title: String
    var done: Bool

    init(title: String, done: Bool) {
        self.title = title
        self.done = done
    }
}

if let data = try? Data(contentsOf: dataFilePath!) {
  let decoder = PropertyListDecoder()
  do {
    itemArray = try decoder.decode([TodoeyItem].self, from: data)

    //Refresh the tableView
    self.tableView.reloadData()
    } catch {
      print("Error decoding item array, \(error)")
    }
} else {
  print("Error decoding item array")
}

import UIKit
import CoreData

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
        // Saves changes in the application's managed object context before the application terminates.
        self.saveContext()
    }


    // MARK: - Core Data stack

    lazy var persistentContainer: NSPersistentContainer = {
        /*
         The persistent container for the application. This implementation
         creates and returns a container, having loaded the store for the
         application to it. This property is optional since there are legitimate
         error conditions that could cause the creation of the store to fail.
         */
        let container = NSPersistentContainer(name: "YOUR_DATA_MODEL_NAME")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

                /*
                 Typical reasons for an error here include:
                 * The parent directory does not exist, cannot be created, or disallows writing.
                 * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                 * The device is out of space.
                 * The store could not be migrated to the current model version.
                 Check the error message to determine what the actual problem was.
                 */
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}

let container = NSPersistentContainer(name: "DataModel")

import Foundation

class TodoeyItem: Codable {
    var title: String
    var done: Bool

    init(title: String, done: Bool) {
        self.title = title
        self.done = done
    }
}

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let newItem = MyTodoeyItem(context: context)
newItem.title = content
newItem.done = false

itemArray.append(newItem)
do {
  try context.save()
} catch {
  if let error = error as NSError? {
    fatalError("Unresolved error \(error), \(error.userInfo)")
  }
}

import CoreData

class TodoListViewController: UITableViewController {
  var itemArray:[MyTodoeyItem] = []
  func loadItems() {
    do {
      let request: NSFetchRequest<MyTodoeyItem> = MyTodoeyItem.fetchRequest()
      itemArray = try context.fetch(request)
      } catch {
        print("Error fetching data from context \(error)")
      }
  }
}

itemArray[indexPath.row].setValue("new value", forKey: "title")
itemArray[indexPath.row].setValue(true, forKey: "done")
do {
  try context.save()
} catch {
  print("Error saving context \(error)")
  }

// Delete data from our Core Data, then call 'context.save()' to save data
context.delete(itemArray[indexPath.row])
do {
  try self.context.save()
} catch {
  print("Error saving context \(error)")
}

// Does nothing for our Core Date, it merely update our itemArray which is used to populate our tableView
itemArray.remove(at: indexPath.row)

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    print(NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).last! as String)
    return true
}

class ViewController: UIViewController {
    var realm: Realm? = nil

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        // MARK: Realm - initialising
        do {
            realm = try Realm()
        } catch {
            NSLog("Error Initialising Realm: \(error)")
        }

        print(Realm.Configuration.defaultConfiguration.fileURL)
    }
}

import Foundation
import RealmSwift

class Category: Object {
    @objc dynamic var name: String = ""
    let items = List<Item>()
}

import Foundation
import RealmSwift

class Item: Object {
    // dynamic is a declaration modifier, it basically tells the runtime to use dynamic dispatch over the standard which is a static dispatch.This allows the property "name" to be monitered for change at runtime.
    @objc dynamic var name: String = ""

    // If we just simpily wrote "Category", then this is just a class. In order to make it the type of "Category", we have to say ",self"
    // property: what the parent list named in Category
    var parentCategory = LinkingObjects(fromType: Category.self, property: "items")
}

do {
    try realm?.write {
        let category = Category()
        category.name = "any category"
        realm?.add(category)
    }
} catch {
    NSLog("Error writing Realm: \(error)")
}

do {
    try realm?.write {
        // do something here
    }
} catch {
    NSLog("Error writing Realm: \(error)")
}

var categories: Results<Category>?
class ViewController: UIViewController {
  override func viewDidLoad() {
        super.viewDidLoad()

        do {
            realm = try Realm()
            categories = realm?.objects(Category.self)
        } catch {
            NSLog("Error Initialising Realm: \(error)")
        }
  }
}

do {
  try realm?.write {
    realm?.delete(category)
    }
  } catch {
    NSLog("Error writing Realm: \(error)")
    }

import Cocoa
import CreateML

let data = try MLDataTable(contentsOf: URL(fileURLWithPath: "/Users/xxx/Workspace/iOS-tutorial/twitter-sanders-apple3.csv"))

// training data : testing data = 80 : 20
let (trainingData, testingData) = data.randomSplit(by: 0.8, seed: 5)

// textColumn and labelColumn depend on the .csv file
let sentimentClassfier = try MLTextClassifier(trainingData: trainingData, textColumn: "text", labelColumn: "class")

// test the model
let evaluationMetrics = sentimentClassfier.evaluation(on: testingData)
let evaluationAccuracy = (1 - evaluationMetrics.classificationError) * 100

// create our own mlmodel
let metadata = MLModelMetadata(author: "Catherine", shortDescription: "A model trained to classify sentiment on Tweets", license: "MIT", version: "0.1")
try sentimentClassfier.write(to: URL(fileURLWithPath: "/Users/xxx/Workspace/iOS-tutorial/tweetSentimentClassifer.mlmodel"), metadata: metadata)

try sentimentClassfier.prediction(from: "@Apple is a terrible company") //Neg
try sentimentClassfier.prediction(from: "I just found the best restaurant ever, and it's @Taco Bell") //Pos
try sentimentClassfier.prediction(from: "I think @CocaCola ads are just ok") //Neutral