Swift

在开发中，经常需要用到协议代理模式。比如，进入编辑页面修改数据后，将新数据回传到主界面。

下面通过一个样例来说明协议代理模式，功能如下：

1，主页面有一个标签和一个修改按钮，点击修改按钮会跳转到编辑页面

2，编辑页面中修改输入框的文字后，点击“确定”则返回主页面，同时主页面的标签值会替换成新值

3，如果点击编辑页面的“取消”按钮则直接返回主页面

效果图如下：

实现过程：

1，首先在storyboard中绘制如下两个界面，同时将主界面的“修改”按钮与编辑页做present modally关联

2，设置编辑页面的Identity为EditView

3，主界面 ViewController.swift

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import UIKit   class ViewController: UIViewController,EditViewControllerDelegate{       @IBOutlet weak var label: UILabel!           override func viewDidLoad() {         super.viewDidLoad()         // Do any additional setup after loading the view, typically from a nib.     }       override func didReceiveMemoryWarning() {         super.didReceiveMemoryWarning()         // Dispose of any resources that can be recreated.     }           //页面跳转时     override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {         if segue.identifier == "EditView"{             //通过seque的标识获得跳转目标             let controller = segue.destinationViewController as EditViewController             //设置代理             controller.delegate = self             //将值传递给新页面             controller.oldInfo = label.text         }     }       func editInfo(controller:EditViewController, newInfo:String){         label.text = newInfo;         //关闭编辑页面         controller.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)     }           func editInfoDidCancer(controller:EditViewController){         //关闭编辑页面         controller.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)     } }

4，编辑页 EditViewController.swift

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import UIKit   class EditViewController: UIViewController {       @IBOutlet weak var textField: UITextField!           var delegate:EditViewControllerDelegate?           var oldInfo:String?           override func viewDidLoad() {         super.viewDidLoad()           // Do any additional setup after loading the view.         if oldInfo  != nil{             textField.text = oldInfo         }     }       override func didReceiveMemoryWarning() {         super.didReceiveMemoryWarning()         // Dispose of any resources that can be recreated.     }       @IBAction func done(sender: AnyObject) {         delegate?.editInfo(self, newInfo: textField.text)     }       @IBAction func cancel(sender: AnyObject) {         delegate?.editInfoDidCancer(self)     } }

5，编辑页代理 EditViewControllerDelegate.swift

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protocol EditViewControllerDelegate{     func editInfo(controller:EditViewController, newInfo:String)     func editInfoDidCancer(controller:EditViewController) }