[英]Sharing data between classes via delegates in Swift, iOS
我试图了解代表在Swift以及一般情况下的工作情况。 在创建的示例中,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,当我从已创建的var recieveMessage
变量实例中调用函数ShareMessage(message: NSString)
时,遇到了var recieveMessage
我必须键入其他消息或字符串,而且无法检索Sender
类发送给它的消息。
这是我正在使用的代码。 我不确定我要问的内容是否正确,但是我只是很好奇如何获取变量实例中的数据。
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.
这是我在message
或数据时遇到的麻烦,因为我必须传递新的参数。
receiveMessage.shareMessage(message: NSString)
我认为您的逻辑有些混乱。
您的发件人被设置为自己创建接收者,然后在创建时立即向其发送消息。
因此,在此行中:
var sendMessage: Sender = Sender(sendersMessage: "Hello Receiver.")
您已经完成了接下来两行中要执行的操作。 如果要让此接收者存储该消息并供以后检索,则需要Receiver类将其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进行访问:
var sharedMessage = receiver.savedMessage
但是,您遇到的第二个问题是,因为您已在发件人内部创建了接收方,所以您需要从接收方中拉出接收方。
var sender: Sender = Sender(sendersMessage: "Hello Receiver.")
var receiver:Receiver = sender.delegate
var sharedMessage = receiver.savedMessage
这是一件很奇怪的事情。 通常的模式是创建一个接收方并将其提供给发送方。 然后在发送方中调用一个函数,该函数将触发一条消息发送到接收方。 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()
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