Swift 協議和委託(代理)，swift委託

Swift 協議和委託(代理)，swift委託

協議 (Protocols)

用於統一方法和屬性的名稱，而不實現任何功能，能夠被類、枚舉、結構體實現，滿足協議要求的都成為協議的遵循者，遵循者需要提供協議指定的成員，如方法，屬性，操作符，下標

文法protocol SomeProtocol {// protocol definition goes here} // 中間以冒號分隔實現協議，有多個協議的話，協議之間逗號分隔struct SomeStructure: FirstProtocol, AnotherProtocol {// structure definition goes here} // 含有父類的同時實現協議，父類寫在協議之前class SomeClass: SomeSuperclass, FirstProtocol, AnotherProtocol {// class definition goes here}

 

委託(代理)模式

委託是一種設計模式，它允許類或結構體將一些需要它們負責的功能交由(委託)給其他的類型。

委託模式的實現很簡單： 定義協議來封裝那些需要被委託的函數和方法， 使其遵循者擁有這些被委託的函數和方法。

委託模式可以用來響應特定的動作或接收外部資料源提供的資料，而無需要知道外部資料源的類型

文法

FirstViewController的代碼

class FirstViewController: UIViewController, SecondViewControllerDelegate {    @IBOutlet weak var showDelegateTextLabel: UILabel!        override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view.    }        //點擊按鈕跳轉到SecondViewController    @IBAction func tapGoSecondViewController(sender: UIButton) {        //從storyboard上載入SecondViewController        let secondVC = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle()).instantiateViewControllerWithIdentifier("secondViewController") as! SecondViewController              secondVC.delegate = self        //跳轉到SecondViewController        self.navigationController?.pushViewController(secondVC, animated: true)    }    //MARK: - SecondViewControllerDelegate    func fetchBackString(str: String) {        self.showDelegateTextLabel.text = str    }        override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }}

 

SecondViewController的代碼

import UIKitprotocol SecondViewControllerDelegate: NSObjectProtocol{    func fetchBackString(str: String)}class SecondViewController: UIViewController {        @IBOutlet weak var inputTextField: UITextField!        weak var delegate: SecondViewControllerDelegate?        override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view.    }    @IBAction func delegateBackMethod(sender: UIButton) {        if self.delegate != nil {            if let tempString = self.inputTextField.text {                delegate!.fetchBackString("代理返回資料:\(tempString)")            }        }        self.navigationController?.popViewControllerAnimated(true)    }        override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }}