如何使用协议/委托在 UIViewControllers 之间传递数据

How to pass data between UIViewControllers with protocols/delegates(如何使用协议/委托在 UIViewControllers 之间传递数据)

问题描述

在下面的代码中，我有一个 ViewController("SenderViewController")，当点击按钮时，它会向主 ViewController 传递一条消息.我不完全理解的是主 ViewController 中的 messageData() 方法如何知道何时监听消息.

In the code below I have a ViewController("SenderViewController"), which passes a message to the main ViewController when a button is tapped. What I don't fully understand is how does messageData() method in the main ViewController know when to listen for the message.

谁能解释一下是什么触发了主 ViewController 中的 messageData() 方法?

Can someone please explain me what is triggering the messageData() method in the main ViewController?

SenderViewController:

SenderViewController:

import UIKit  
protocol SenderViewControllerDelegate {  
    func messageData(data: AnyObject)  
}  
class SenderViewController: UIViewController {  
    @IBOutlet weak var inputMessage: UITextField!  
     var delegate: SenderViewControllerDelegate?  

    @IBAction func sendData(sender: AnyObject) {  
        /  
        if inputMessage.text != ""{  
            self.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)  
            self.delegate?.messageData(inputMessage.text!)  
        }  
    }  
}  

主视图控制器:

import UIKit  
class ViewController: UIViewController, SenderViewControllerDelegate{  
    @IBOutlet weak var showData: UILabel!  

    override func viewDidLoad() {  
        super.viewDidLoad()  
    }  

    @IBAction func goToView(sender: AnyObject) {  
        let pvc = storyboard?.instantiateViewControllerWithIdentifier("senderViewController") as! SenderViewController  
        pvc.delegate = self  
        self.presentViewController(pvc, animated:true, completion:nil)  
    }  

   // What triggers this method, how it know when to listen? 
    func messageData(data: AnyObject) {  
        self.showData.text = "(data)"  
    }  
} 

非常感谢！

推荐答案

对象并不完全监听方法调用.他们坐在那里，等待被调用.

Objects don't exactly listen for method calls. They sit there, waiting to invoked.

线

self.delegate?.messageData(inputMessage.text!)

从您的 SenderViewController 是一个函数调用.(虽然 method 通常用于对象的功能，但术语方法和函数几乎可以互换.)它调用 ViewController 中的函数 messageData.

From your SenderViewController is a function call. (The term method and function are pretty much interchangeable, although the method is usually used for the functions of objects.) It invokes the function messageData in ViewController.

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