Swift利用閉包（closure）來實現傳值-->前後兩個控制器的反向傳值

利用了大約一個多小時來搞明白OC中Blocks反向傳值和Swift中Closure反向傳值的差別，下面直接貼上代碼：

一、第一個界面

//  Created by 秦志偉 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:"下一頁",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)
        //將當前someFunctionThatTakesAClosure函數指針傳到第二個界面，第二個界面的閉包拿到該函數指針後會進行回調該函數
        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、第二個界面

//  Created by 秦志偉 on 14-6-13.
import UIKit
//類似於OC中的typedef
typealias sendValueClosure=(string:String)->Void
class ZWSecondViewController: UIViewController {
    var i:Int?
    //聲明一個閉包
    var myClosure:sendValueClosure?
    //下面這個方法需要傳入上個界面的someFunctionThatTakesAClosure函數指針
    func initWithClosure(closure:sendValueClosure?){
        //將函數指針賦值給myClosure閉包，該閉包中涵蓋了someFunctionThatTakesAClosure函數中的局部變量等的引用
        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("點擊我" ,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{
            //閉包隱式調用someFunctionThatTakesAClosure函數：回調。
            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.
    }
    */

}

轉載請註明！！！，歡迎加入iOS交流羣：愛瘋、愛Coding：209476515