[英]Protocol Delegate Method is not called in Swift
不调用协议委托方法..
第一个视图控制器代码
class ViewController: UIViewController,customDelegate {
var seconviewcontroller : SecondViewController = SecondViewController()
@IBOutlet weak var Label: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
seconviewcontroller.delegate = self
}
func didSelectData(_ result: String) {
Label.text = result
print("Didselect Data Call")
}
第二个视图控制器代码
import UIKit
protocol customDelegate: class {
func didSelectData(_ result: String)
}
class SecondViewController: UIViewController {
var delegate: customDelegate?
@IBOutlet weak var secondbutton: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
}
@IBAction func secondbuttonclick(_ sender: Any) {
let selectedItem = "naga"
delegate?.didSelectData(selectedItem)
}
如何调用 func didSelectData 请帮帮我
因为您已经使用 segue 在视图之间导航。 您也可以在此示例中使用它。 我提供以下代码示例,以便您可以自行跟踪以检测代码中的问题。
第一个视图控制器
import UIKit
class ViewController: UIViewController, SecondVCDelegate {
@IBOutlet weak var label: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let secondVC = segue.destination as? SecondViewController {
secondVC.delegate = self
}
}
func didSelectData(_ result: String) {
label.text = result
print(result)
}
}
第二个视图控制器
import UIKit
protocol SecondVCDelegate: class {
func didSelectData(_ result: String)
}
class SecondViewController: UIViewController {
@IBOutlet weak var button: UIButton!
weak var delegate: SecondVCDelegate?
override func viewDidLoad() {
super.viewDidLoad()
}
@IBAction func buttonTapped(_ sender: UIButton) {
delegate?.didSelectData("My result")
dismiss(animated: true, completion: nil)
}
}
所以基本上在行var seconviewcontroller : SecondViewController = SecondViewController()
与您推送的视图控制器实例不同。
您正在制作SecondViewController
一个单独实例,因此您在推送这样的 pushes 对象时已经完成了委托 self
let secondVCInstance = self.storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
secondVCInstance.delegate = self
self.navigationController?.pushViewController(secondVCInstance, animated: true)
注意: - 每个对象都有自己的属性
第一个视图控制器
import UIKit
class ViewController: UIViewController, SecondVCDelegate {
@IBOutlet weak var label: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let secondVC = segue.destination as? SecondViewController {
secondVC.delegate = self
}
}
func didSelectData(_ result: String) {
label.text = result
print(result)
}
}
第二个视图控制器
import UIKit
protocol SecondVCDelegate: class {
func didSelectData(_ result: String)
}
class SecondViewController: UIViewController {
@IBOutlet weak var button: UIButton!
weak var delegate: SecondVCDelegate?
override func viewDidLoad() {
super.viewDidLoad()
}
@IBAction func buttonTapped(_ sender: UIButton) {
delegate?.didSelectData("My result")
dismiss(animated: true, completion: nil)
}
}
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