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[操作系统]Swift 使用代理和闭包(closure)反向传值


FirstViewController的代码


import UIKitclass FirstViewController: UIViewController, SecondViewControllerDelegate { @IBOutlet weak var showTextLabel: UILabel! @IBOutlet weak var showDelegateTextLabel: UILabel! override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view. } //点击按钮跳转到SecondViewController @IBAction func tapGoSecondViewController(sender: UIButton) { //从storyboard上加载SecondViewController let secondVC = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle()).instantiateViewControllerWithIdentifier("secondViewController") as! SecondViewController //实现回调,获取回调回来的值 (闭包) secondVC.backClosure = { (backStr: String) -> Void in self.showTextLabel.text = backStr } secondVC.delegate = self //跳转到SecondViewController self.navigationController?.pushViewController(secondVC, animated: true) } //MARK: - SecondViewControllerDelegate(代理) func fetchBackString(str: String) { self.showDelegateTextLabel.text = str } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. }}

SecondViewController的代码

import UIKit//定义闭包类型(特定的函数类型函数类型)typealias InputClosureType = (String) -> Voidprotocol SecondViewControllerDelegate: NSObjectProtocol{  func fetchBackString(str: String)}class SecondViewController: UIViewController {    @IBOutlet weak var inputTextField: UITextField!  //接收上个页面传过来的闭包块  var backClosure: InputClosureType?  weak var delegate: SecondViewControllerDelegate?    override func viewDidLoad() {    super.viewDidLoad()    // Do any additional setup after loading the view.  }  @IBAction func tapBackButton(sender: UIButton) {    if self.backClosure != nil {      if let tempString = self.inputTextField.text {        self.backClosure!(tempString)      }    }    self.navigationController?.popViewControllerAnimated(true)  }    @IBAction func delegateBackMethod(sender: UIButton) {    if self.delegate != nil {      if let tempString = self.inputTextField.text {        delegate!.fetchBackString("代理返回数据:\(tempString)")      }    }    self.navigationController?.popViewControllerAnimated(true)  }    override func didReceiveMemoryWarning() {    super.didReceiveMemoryWarning()    // Dispose of any resources that can be recreated.  }}

效果视图: