Question

我试图了解代理如何在Swift中运行得更好，总的来说。在我创建的示例中，我有一个Sender类和一个Receiver类。我想从Sender向Receiver

发送消息

然后，我想创建Receiver类的变量实例，并打印Sender发送给它的消息。但是当我从我创建的变量实例ShareMessage(message: NSString)调用函数var recieveMessage时，我遇到了困难，我必须输入另一个消息或字符串，我无法检索Sender的消息发给它的课。

这是我正在使用的代码。我不确定我所询问的内容是否正确，但我对如何检索变量实例中的数据感到好奇。

import UIKit

// Protocol to send message between classes.
protocol SendersMessageDelegate{

    func shareMessage(message: NSString)
}

// Class that sends the message
class Sender{

    // Create variable to hold message
    var sendersMessage: NSString = NSString()

    var delegate: SendersMessageDelegate? = Receiver()

    // Grab the message when initialized and send to delegate
    init(sendersMessage: NSString){

        self.sendersMessage = sendersMessage
        delegate?.shareMessage(sendersMessage)
    }          

}

//Class receiving the message
class Receiver: SendersMessageDelegate{

    func shareMessage(message: NSString) {

        println(message)

    }
}

//Create variable instance of sender and send message in initializer.
var sendMessage: Sender = Sender(sendersMessage: "Hello Receiver.")

var receiveMessage: Receiver = Receiver()
receiveMessage.shareMessage(message: NSString) <---- //Can't retrieve message as need new argument for function call.

我无法检索message或数据，因为我必须传递一个新参数。

receiveMessage.shareMessage(message: NSString)

Answer 1

我认为你的逻辑有些混乱。

您的发件人已设置为自行创建接收器，然后在创建时立即向其发送消息。

所以在这一行：

var sendMessage: Sender = Sender(sendersMessage: "Hello Receiver.")

您已经完成了接下来两行中您尝试做的事情。如果你想让这个接收器存储消息并让你稍后检索，那么你需要你的Receiver类将它保存为变量并打印出来。

class Receiver: SendersMessageDelegate{

    var savedMessage:NSString?

    func shareMessage(message: NSString) {
        savedMessage = message
        println(message)
    }
}

然后您可以通过执行以下操作来访问：

var sharedMessage = receiver.savedMessage

然而，您遇到的第二个问题是，因为您已经在发件人中创建了接收器，所以您需要从接收器中拔出接收器。

var sender: Sender = Sender(sendersMessage: "Hello Receiver.")
var receiver:Receiver = sender.delegate
var sharedMessage = receiver.savedMessage

这是一件非常奇怪的事情。通常的模式是创建一个Receiver并将其提供给Sender。然后调用发件人中的一个函数，该函数将触发发送给Receiver的消息。像这样：

import UIKit

// Protocol to send message between classes.
protocol SendersMessageDelegate{
    func shareMessage(message: NSString)
}

// Class that sends the message
class Sender{

    // Create variable to hold message
    var sendersMessage: NSString = NSString()

    var delegate: SendersMessageDelegate?

    // Save the message that it needs to send
    init(sendersMessage: NSString){
        self.sendersMessage = sendersMessage
    }

    // If it has as a delegate, then share the message with it.
    func sendMessage() {
        delegate?.shareMessage(sendersMessage)
    }
}

//Class receiving the message
class Receiver: SendersMessageDelegate{

    var savedMessage:NSString?

    func shareMessage(message: NSString) {
        savedMessage = message
        println(message)
    }
}

//Create Sender and Receiver
var sender: Sender = Sender(sendersMessage: "Hello Receiver.")
var receiver: Receiver = Receiver()

//give Sender it's Receiver
sender.delegate = receiver

//Trigger the sender to send message to it's Receiver
sender.sendMessage()

通过Swift，iOS中的代理在类之间共享数据

1 个答案: