Unwrapping the UILabel error while implementing Delegate and Protocols - ios

Question

Here I am getting error when unwrapping the del UIlabel
#IBOutlet weak var del: UILabel! // my label must change through protocol implementation
del.text = name // error here
Unexpectedly found nil while implicitly unwrapping an Optional value
ViewController.swift
class ViewController: UIViewController,DataPass {
#IBOutlet weak var del: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func seconeView(_ sender: UIButton) {
let selview = storyboard?.instantiateViewController(withIdentifier: "SecondViewController")as!SecondViewController
present(selview,animated: true,completion: nil)
}
func pass(name: String) {
del.text = name // error here Unexpectedly found nil while implicitly unwrapping an Optional value
}
}
SecondViewController.swift
protocol DataPass {
func pass(name:String)
}
class SecondViewController: UIViewController {
let delegate:DataPass! = ViewController()
let label = "Delegate"
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func endView(_ sender: UIButton) {
if let del = delegate {
del.pass(name: label)
} else {
print("Delegate property is not set")
}
dismiss(animated: true, completion: nil)
}
}

Answer 1

There are few changes you need to do to make your delegate working:
In second controller make these changes:
protocol DataPass {
func pass(name:String)
}
class SecondViewController: UIViewController {
var delegate:DataPass?
let label = "Delegate"
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func endView(_ sender: UIButton) {
if let del = delegate {
del.pass(name: label)
} else {
print("Delegate property is not set")
}
dismiss(animated: true, completion: nil)
}
}
and in first controller :
class ViewController: UIViewController,DataPass {
#IBOutlet weak var del: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func seconeView(_ sender: UIButton) {
let selview = storyboard?.instantiateViewController(withIdentifier: "SecondViewController")as!SecondViewController
selview.delegate = self
present(selview,animated: true,completion: nil)
}
func pass(name: String) {
del.text = name
}
}
Explanation:
In this line let delegate:DataPass! = ViewController() you are creating another instance for your delegate variable which doesn't hold any label. You need to assign your ViewController's instance while presenting the next controller to make it working.