How to change value of variable by UISwitch? - ios

Question

I am a beginner to Xcode and Swift and I am currently creating an application where the user adds a person on the application and after that it right the amount of money they owe that person or that person owes him/her.
Note: I have used core data to store all the value
I actually want to change the value of a variable when switch is on and off. For instance, in the following I want the "amount" to be negative when the switch is on and positive when it is off. Also, when I try to do this and send amount variable to previous view controller I can't send the value depending on the UISwitch because it always shows positive. I am trying to find a solution to this from past 3 days therefore can you please help me? Thanks a lot in advance
Owe ViewController
import UIKit
class NewOweTableViewController: UIViewController {
#IBOutlet weak var titleTextField: UITextField!
#IBOutlet weak var locationTextField: UITextField!
#IBOutlet weak var amountTextField: UITextField!
#IBOutlet weak var datePicker: UIDatePicker!
let context = (UIApplication.shared.delegate as!
AppDelegate).persistentContainer.viewContext
var owe: Owe?
var dataInfo: [Owe] = []
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.navigationBar.viewWithTag(1)?.isHidden = true
let saveBTN = UIBarButtonItem(barButtonSystemItem:UIBarButtonSystemItem.save, target:self,
action: #selector(saveButtonTapped(_:)))
let deleteBTN = UIBarButtonItem(barButtonSystemItem:UIBarButtonSystemItem.trash, target:self,
action: #selector(deleteButtonTapped(_:)))
self.navigationItem.rightBarButtonItems = [saveBTN, deleteBTN]
if !dataInfo.isEmpty {
titleTextField.text = dataInfo[0].name
amountTextField.text = (NSString(format: "%.2f", (dataInfo[0].amount) as CVarArg) as String)
locationTextField.text = dataInfo[0].location
datePicker.date = dataInfo[0].date!
}
}
#objc func saveButtonTapped(_ sender: UIButton){
if !dataInfo.isEmpty{
let data = dataInfo[0]
data.name = titleTextField.text
data.amount = Double(amountTextField.text!)!
data.location = locationTextField.text
data.date = datePicker.date
}
else if titleTextField.text == "" || amountTextField.text == "" || locationTextField.text == "" {
return
}
else{
let data = Owe(context: context)
data.name = titleTextField.text
data.amount = Double(amountTextField.text!)!
data.location = locationTextField.text
data.date = datePicker.date
}
do {
try context.save()
navigationController?.popViewController(animated: true)
} catch {
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
#objc func deleteButtonTapped(_ sender: UIButton){
if !dataInfo.isEmpty{
let data = dataInfo[0]
context.delete(data)
do {
try context.save()
navigationController?.popViewController(animated: true)
} catch {
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
#IBAction func oweSwitch(_ sender: UISwitch) {
if sender.isOn {
owe?.amount = (owe?.amount)! * (-1)
amountTextField.textColor = UIColor.green
} else {
owe?.amount = (owe?.amount)! * (1)
amountTextField.textColor = UIColor.red
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
Previous View Controller
import UIKit
class PersonDetailTableViewController: UITableViewController {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
var totalLabel: UILabel?
var person: People?
var owe: Owe?
#IBOutlet var personTable: UITableView!
var dataInfo: [Owe] = []
var selectedObject: [Owe] = []
var balanceAmount = "Balance: "
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return (dataInfo.count)
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = personTable
.dequeueReusableCell(withIdentifier: "detailsCell", for: indexPath)
cell.textLabel?.text = dataInfo[indexPath.row].name
cell.detailTextLabel?.text = "₹ \(dataInfo[indexPath.row].amount)"
if dataInfo[indexPath.row].amount < 0 {
cell.detailTextLabel?.textColor = UIColor.red
} else {
cell.detailTextLabel?.textColor = UIColor.green
}
return cell
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
selectedObject = [dataInfo[indexPath.row]]
performSegue(withIdentifier: "addOweDetails", sender: nil)
tableView.deselectRow(at: indexPath, animated: true)
}
override func viewDidLoad() {
super.viewDidLoad()
getData()
personTable.dataSource = self
addTotalToNav()
print(dataInfo as Any)
}
// MARK: - Table view data source
func addTotalToNav() -> Void {
if let navigationBar = self.navigationController?.navigationBar {
let totalFrame = CGRect(x: 10, y: 0, width: navigationBar.frame.width/2, height: navigationBar.frame.height)
totalLabel = UILabel(frame: totalFrame)
totalLabel?.text = balanceAmount
totalLabel?.tag = 1
totalLabel?.font = UIFont.boldSystemFont(ofSize: 14)
totalLabel?.textColor = UIColor.red
// navigationBar.large = totalLabel?.text
self.title = totalLabel?.text
}
}
func getData() -> Void {
do{
dataInfo = try context.fetch(Owe.fetchRequest())
var total:Double = 0.00
for i in 0 ..< dataInfo.count {
total += dataInfo[i].amount as! Double
}
balanceAmount = "Balance: ₹" + (NSString(format: "%.2f", total as CVarArg) as String)
}
catch{
print("Fetching Failed")
}
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let vc = segue.destination as! NewOweTableViewController
vc.dataInfo = selectedObject
selectedObject.removeAll()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
getData()
personTable.reloadData()
if (self.navigationController?.navigationBar.viewWithTag(1)?.isHidden == true){
self.navigationController?.navigationBar.viewWithTag(1)?.removeFromSuperview()
addTotalToNav()
}
}
}
Core Data for owe
import UIKit
import CoreData
#objc(Owe)
public class Owe: NSManagedObject {
var date: Date? {
get{
return rawDate as Date?
}
set {
rawDate = newValue as NSDate?
}
}
convenience init?(name: String?, location: String?, amount: Double, date: Date?) {
let appDelegate = UIApplication.shared.delegate as? AppDelegate
guard let context = appDelegate?.persistentContainer.viewContext
else {
return nil
}
self.init(entity: Owe.entity(), insertInto: context)
self.name = name
self.location = location
self.amount = amount
self.date = date
}
}

Answer 1

Hi there and welcome to the Swift Community!
If I understand correctly, you are trying to propagates updates backwards from NewOweTableViewController to PersonDetailTableViewController. If that is the case, an easy way to achieve this with your MVC architecture is by passing a closure to NewOweTableViewController when you initialize it in PersonDetailTableViewController.
In order to do so,
Update NewOweTableViewController and add a closure property.
class NewOweTableViewController: UIViewController {
// ...
var switchValueUpdate: ((Bool) -> ())?
// ...
}
Make sure you call this closure inside your #IBAction that you link to your switch in NewOweTableViewController
#IBAction func oweSwitch(_ sender: UISwitch) {
if sender.isOn {
owe?.amount = (owe?.amount)! * (-1)
amountTextField.textColor = UIColor.green
} else {
owe?.amount = (owe?.amount)! * (1)
amountTextField.textColor = UIColor.red
}
switchValueUpdate?(sender.isOn)
}
update PersonDetailTableViewController to set the closure
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let vc = segue.destination as! NewOweTableViewController
vc.dataInfo = selectedObject
selectedObject.removeAll()
vc.switchValueUpdate = { (isOn) in
// Here you go, update PersonDetailTableViewController to reflect changes related to the switch!
}
}
That's it! Let me know if you have any question on that code, hope it helps!