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

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

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

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