Swift利用闭包（closure）来实现传值-->前后两个控制器的反向传值

利用了大约一个多小时来搞明确OC中Blocks反向传值和Swift中Closure反向传值的区别，以下直接贴上代码：

一、第一个界面

//  Created by 秦志伟 on 14-6-13.
import UIKit

class ZWRootViewController: UIViewController {

init(nibName nibNameOrNil: String?

, bundle nibBundleOrNil: NSBundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
// Custom initialization
}
var myLabel:UILabel?
override func viewDidLoad() {
super.viewDidLoad()

var item = UIBarButtonItem(title:"下一页",style:UIBarButtonItemStyle.Plain,target:self,action:"nextBtnClicked")
self.navigationItem.rightBarButtonItem = item

myLabel = UILabel(frame:CGRectMake(0,100,320,50))
myLabel!.text = "Closure"
myLabel!.textAlignment = NSTextAlignment.Center
self.view.addSubview(myLabel!)
// Do any additional setup after loading the view.
}
func someFunctionThatTakesAClosure(string:String) -> Void {
// function body goes here
myLabel!.text = string
}
func nextBtnClicked(){
let second = ZWSecondViewController(nibName:nil,bundle:nil)
//将当前someFunctionThatTakesAClosure函数指针传到第二个界面，第二个界面的闭包拿到该函数指针后会进行回调该函数
second.initWithClosure(someFunctionThatTakesAClosure)
self.navigationController.pushViewController(second,animated:true)

}

override func viewWillDisappear(animated: Bool){
myLabel!.hidden = true
}
override func viewWillAppear(animated: Bool){
myLabel!.hidden = false
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}

/*
// #pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue?

, sender: AnyObject?) {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/

}

二、第二个界面

//  Created by 秦志伟 on 14-6-13.
import UIKit
//相似于OC中的typedef
typealias sendValueClosure=(string:String)->Void
class ZWSecondViewController: UIViewController {
var i:Int?

//声明一个闭包
var myClosure:sendValueClosure?
//以下这种方法须要传入上个界面的someFunctionThatTakesAClosure函数指针
func initWithClosure(closure:sendValueClosure?

){
//将函数指针赋值给myClosure闭包，该闭包中涵盖了someFunctionThatTakesAClosure函数中的局部变量等的引用
myClosure = closure
}

init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?

) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)

// Custom initialization
}

override func viewDidLoad() {
super.viewDidLoad()
i = 0
var btn = UIButton.buttonWithType(UIButtonType.System) as?UIButton
btn!.frame = CGRectMake(0,100,320,50)
btn!.setTitle("点击我" ,forState:UIControlState.Normal)
btn!.addTarget(self,action:"action", forControlEvents:UIControlEvents.TouchUpInside)
self.view.addSubview(btn)

// Do any additional setup after loading the view.
}
func action(){
i = i!+1
//判空
if myClosure{
//闭包隐式调用someFunctionThatTakesAClosure函数：回调。
myClosure!(string: "好好哦\(i)")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}

/*
// #pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue?

, sender: AnyObject?

) {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/

}

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