TextField unloads value when navigating in Swift - ios

Question

I have two ViewControllers, each with one TextField to get user input number and two buttons to calculate and navigate.
The instance of TextField in the SecondVC is created by user when filling the TextFields and it exists and it is shown in the View
The problem is: when you leave the SecondView Controller after creating the object - Cell and you come back to it later, it is set back to cero, which is not the instance - Cell value
class MainViewController: UIViewController {
#IBOutlet weak var A3TextField: UITextField!
#IBAction func calc(_ sender: Any) {
let A3 = Cell(name: "A3", sheet: "", value: Double(A3TextField.text!)!)
print(A3)
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
}
class SecondViewController: UIViewController {
#IBOutlet weak var B3TextField: UITextField!
#IBAction func calc2(_ sender: Any) {
let B3 = Cell(name: "B3", sheet: "", value: Double(B3TextField.text!)!)
print(B3)
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
}
struct Cell {
var name: String = ""
var sheet: String = ""
var value: Double = 0
init(name: String, sheet: String, value: Double) {
self.name = name
self.sheet = sheet
self.value = value
}
}

Answer 1

When controller pop or push ,their temporary property value or object can not be save to other controller,even in itself controller ,when push and back ,their are the init value,if you want save value when page switching，suggest these solution:
1. Pass throw the attribute values(one => two)
OneViewController:
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let twoVC = storyboard.instantiateViewController(withIdentifier: "TwoViewControllerID") as! twoViewController
twoVC.myStr="Controller one to controller two!"
self.present(twoVC, animated: true, completion: nil)
TwoViewController
var myStr=String()
override func viewDidLoad() {
super.viewDidLoad()
print("get value：\(myStr)"
}
2, use NSUerDfault to save and get
SetValue:
let userDefault = UserDefaults.standard
userDefault.set(name, forKey: "name")
userDefault.synchronize()
GetValue:
let userDefault = UserDefaults.standard
let name = userDefault.object(forKey: "name") as? String
3,storybord pass value(one => two)
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let theSegue=segue.destination as! twoViewController theSegue.myStr="other pass way" }
4,deleagte pass value(two => one)
based don back to front page
TwoViewController:
//(1)create a delegate before class
protocol FTVCdelegte : NSObjectProtocol{
//define method
// one method
func change(title:String)
//two method
func ChangeColoer (Coloer:UIColor)
//three method
func ChangSucces(YON:Bool)
}
//(2)create delegate object。
var delegate_zsj:FTVCdelegte?
//(3)click back button
#IBAction func backBtnAction(_ sender: UIButton) {
delegate_zsj?.change(title: "main page")
delegate_zsj?.ChangeColoer(Coloer: UIColor.red)
delegate_zsj?.ChangSucces(YON: true)
self.navigationController?.popViewController(animated: true)
}
OneViewController
//(4)inherit delegate：
class SecondViewController: UIViewController,FTVCdelegte,ChangeBtnDelege{
...
//(5)imple delegate method
func change(title: String) { self.title = title }
func ChangeColoer(Coloer: UIColor) { self.view.backgroundColor = Coloer }
func ChangSucces(YON: Bool) { print(YON) }
//(6)when pop page use
#IBAction func tiaozhuanBtnAction(_ sender: Any) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let oneVC = storyboard.instantiateViewController(withIdentifier: "OneViewControllerID") as! oneViewController
oneVC.delegate_zsj = self
self.navigationController?.pushViewController(oneVC, animated: true)
}
5,block pass value(two => one)
based don back to front page
TwoViewController:
//(1)define a block method：
var bbchange:((_ title:String,_ myColor:UIColor)->Void)?
//(2)back to front page：
#IBAction func backBtnAction(_ sender: UIButton) {
bbchange?("document",UIColor.green)
self.navigationController?.popViewController(animated: true)
}
OneViewController
//(3)next page invoke block method
#IBAction func tiaozhuanBtnAction(_ sender: Any) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let threeVC = storyboard.instantiateViewController(withIdentifier: "twoViewControllerID") as! twoViewController
twoVC.bbchange=
{
( title:String,myColor:UIColor) in
self.title=title
self.view.backgroundColor=myColor
}
self.navigationController?.pushViewController(twoVC, animated: true)
}