Delegate between controllers doesn't work. Why? - ios

Question

I try to use delegate to send data from textField which is in the Detail2(ViewController) to array which is in the ViewController.
I used here print method and first print show that one element has been added to the array but the second print method which is below the ViewVillAppear() show that array is empty. How? I want to be able to to use delegate to add data to my table.
["sdsd"] First print from the console
[]Second print from the console
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
#IBOutlet var add: UIBarButtonItem!
#IBOutlet var tv: UITableView!
var array :[String] = []
override func viewDidLoad() {
super.viewDidLoad()
tv.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "segue" {
let vc: Detail2 = segue.destination as! Detail2
vc.delegate = self
}
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return array.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
cell.textLabel?.text = array[indexPath.row]
return cell
}
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
array.remove(at: indexPath.row )
tv.reloadData()
}
}
func alert () {
}
override func viewWillAppear(_ animated: Bool) {
tv.reloadData()
print(array)
}
}
extension ViewController: Data {
func tekst(data: String) {
array.append(data)
print(array)
}
}
and Detail2
protocol Data {
func tekst (data: String)
}
class Detail2: UIViewController {
var delegate: Data? = nil
#IBAction func btn(_ sender: Any) {
let sb = storyboard?.instantiateViewController(withIdentifier: "Main" ) as! ViewController
navigationController?.pushViewController(sb, animated: true)
if delegate != nil {
if txtfield.text != nil {
let napis = txtfield.text
delegate?.tekst(data: napis!)
}
}
}
#IBOutlet var btn: UIButton!
#IBOutlet var txtfield: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
btn.backgroundColor = UIColor.blue
btn.tintColor = UIColor.white
btn.layer.cornerRadius = 25
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 1

Just update your function with:
#IBAction func btn(_ sender: Any) {
if delegate != nil {
if txtfield.text != nil {
let napis = txtfield.text
delegate?.tekst(data: napis!)
}
navigationController?.popViewController(animated: true)
}
}
Update:
extension ViewController: Data {
func tekst(data: String) {
array.append(data)
print(array)
self.tv.reloadData()
}
}

Answer 2

You need to add this delegate?.tekst(data: napis!) inside completion handler, because you are using navigationController, there is no option for completion handler,So have to add UINavigationController extension like that:
extension UINavigationController {
public func pushViewController(viewController: UIViewController,
animated: Bool,
completion: (() -> Void)?) {
CATransaction.begin()
CATransaction.setCompletionBlock(completion)
pushViewController(viewController, animated: animated)
CATransaction.commit()
}
}
change this
navigationController?.pushViewController(sb, animated: true){
if delegate != nil {
if txtfield.text != nil {
let napis = txtfield.text
delegate?.tekst(data: napis!)
}

Answer 3

Update your code in Detail2 viewcontroller
#IBAction func btn(_ sender: Any) {
if delegate != nil {
if txtfield.text != nil {
let napis = txtfield.text
delegate?.tekst(data: napis!)
}
}
navigationController?.popViewController(animated: true)
}

Answer 4

In the ViewController implement the delegate method
func tekst (data: String) {
array.append(data)
}
// in detail
#IBAction func btn(_ sender: Any) {
if txtfield.text != nil {
let napis = txtfield.text
delegate?.tekst(data: napis!)
}
/// dismiss detail here don't push main again
self.navigationController?.popViewController(animated: true)
}