[Swift] Vaguely grasp the flow of Delegate

What is delegation?

It's getting complicated when I think about it, but I vaguely grasp the flow.

Delegation side

** side that asks ** to use the method ".


// 1.Set rules
protocol CatchProtocol {
  func catchData(count:Int)

class NextViewController: UIViewController {

  var count:Int = 0

  // 2.Make 1 a variable named deledele
  var deledele:CatchProtocol?

  @IBAction func push(_ sender: Any) {
    // 3.Activate. Pass arguments if needed


The ** side who is asked ** to use the method.


// 1.declare
class ViewController: UIViewController, CatchProtocol {

  @IBOutlet weak var label: UILabel!
  var count:Int = 0
  override func viewDidLoad() {

  // 2.Delegate method. Created by pressing fix with an error when declaring
  func catchData(count: Int) {
    label.text = String(count)
  @IBAction func next(_ sender: Any) {
    performSegue(withIdentifier: "next", sender: nil)
  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    let nextVC = segue.destination as! NextViewController

    //The description "I was entrusted with the deledele of NextViewController"
    nextVC.deledele = self

――It's really easier to understand when other people such as team members see it if you use delegate instead of deledele. ――I understand the flow somehow, but the last self is vague

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