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，设置这个关联Segue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
)
}
}
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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
)
}
}
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5，编辑页代理 EditViewControllerDelegate.swift
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protocol
EditViewControllerDelegate
{
func
editInfo(controller:
EditViewController
,newInfo:
String
)
func
editInfoDidCancer(controller:
EditViewController
)
}
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6，在Storyboard中，将编辑页的Class设为EditViewController
presentingViewController：The view controller that presented this view controller. (read-only)，present出来本视图控制器的视图控制器
如A-->弹出B,则A.presentedViewController = B
B.presentingViewController = A
dismissViewControllerAnimated:YES
dismisses the view controller that was presented modally by the view controller.
也就是在在A上调该方法，dismiss掉A弹出的vc
如果在B上调，会调用presenting view的该方法，即A的该方法