Swift 使用代理和闭包(closure)反向传值

FirstViewController的代码

import UIKit

class FirstViewController: UIViewController, SecondViewControllerDelegate {

@IBOutlet weak var showTextLabel: UILabel!
@IBOutlet weak var showDelegateTextLabel: UILabel!

override func viewDidLoad() {
super.viewDidLoad()

// Do any additional setup after loading the view.
}

//点击按钮跳转到SecondViewController
@IBAction func tapGoSecondViewController(sender: UIButton) {
//从storyboard上加载SecondViewController
let secondVC = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle()).instantiateViewControllerWithIdentifier("secondViewController") as! SecondViewController
//实现回调，获取回调回来的值 （闭包）
secondVC.backClosure = {
(backStr: String) -> Void in
self.showTextLabel.text = backStr
}
secondVC.delegate = self
//跳转到SecondViewController
self.navigationController?.pushViewController(secondVC, animated: true)
}
//MARK: - SecondViewControllerDelegate(代理)
func fetchBackString(str: String) {
self.showDelegateTextLabel.text = str
}

override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

SecondViewController的代码

import UIKit

//定义闭包类型（特定的函数类型函数类型）
typealias InputClosureType = (String) -> Void

protocol SecondViewControllerDelegate: NSObjectProtocol{
func fetchBackString(str: String)
}

class SecondViewController: UIViewController {

@IBOutlet weak var inputTextField: UITextField!
//接收上个页面传过来的闭包块
var backClosure: InputClosureType?
weak var delegate: SecondViewControllerDelegate?

override func viewDidLoad() {
super.viewDidLoad()

// Do any additional setup after loading the view.
}

@IBAction func tapBackButton(sender: UIButton) {
if self.backClosure != nil {
if let tempString = self.inputTextField.text {
self.backClosure!(tempString)
}
}
self.navigationController?.popViewControllerAnimated(true)
}

@IBAction func delegateBackMethod(sender: UIButton) {
if self.delegate != nil {
if let tempString = self.inputTextField.text {
delegate!.fetchBackString("代理返回数据:\(tempString)")
}
}
self.navigationController?.popViewControllerAnimated(true)
}

override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

效果视图：